env: Rename getenv/_f() to env_get()

We are now using an env_ prefix for environment functions. Rename these
two functions for consistency. Also add function comments in common.h.

Quite a few places use getenv() in a condition context, provoking a
warning from checkpatch. These are fixed up in this patch also.

Suggested-by: Wolfgang Denk <wd@denx.de>
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/usb/gadget/designware_udc.c b/drivers/usb/gadget/designware_udc.c
index 0db7a3b..a25f501 100644
--- a/drivers/usb/gadget/designware_udc.c
+++ b/drivers/usb/gadget/designware_udc.c
@@ -601,7 +601,7 @@
 	if ((ep != 0) && (udc_device->device_state < STATE_ADDRESSED))
 		return;
 
-	tt = getenv("usbtty");
+	tt = env_get("usbtty");
 	if (!tt)
 		tt = "generic";
 
diff --git a/drivers/usb/gadget/ether.c b/drivers/usb/gadget/ether.c
index d010537..2cf5c8d 100644
--- a/drivers/usb/gadget/ether.c
+++ b/drivers/usb/gadget/ether.c
@@ -2384,12 +2384,12 @@
 	strlcpy(host_addr, CONFIG_USBNET_HOST_ADDR, sizeof(host_addr));
 #endif
 	/* Check if the user overruled the MAC addresses */
-	if (getenv("usbnet_devaddr"))
-		strlcpy(dev_addr, getenv("usbnet_devaddr"),
+	if (env_get("usbnet_devaddr"))
+		strlcpy(dev_addr, env_get("usbnet_devaddr"),
 			sizeof(dev_addr));
 
-	if (getenv("usbnet_hostaddr"))
-		strlcpy(host_addr, getenv("usbnet_hostaddr"),
+	if (env_get("usbnet_hostaddr"))
+		strlcpy(host_addr, env_get("usbnet_hostaddr"),
 			sizeof(host_addr));
 
 	if (!is_eth_addr_valid(dev_addr)) {
@@ -2420,8 +2420,8 @@
 	gadget = dev->gadget;
 	usb_gadget_connect(gadget);
 
-	if (getenv("cdc_connect_timeout"))
-		timeout = simple_strtoul(getenv("cdc_connect_timeout"),
+	if (env_get("cdc_connect_timeout"))
+		timeout = simple_strtoul(env_get("cdc_connect_timeout"),
 						NULL, 10) * CONFIG_SYS_HZ;
 	ts = get_timer(0);
 	while (!dev->network_started) {
diff --git a/drivers/usb/gadget/f_dfu.c b/drivers/usb/gadget/f_dfu.c
index dfa4359..bc4be71 100644
--- a/drivers/usb/gadget/f_dfu.c
+++ b/drivers/usb/gadget/f_dfu.c
@@ -725,7 +725,7 @@
 
 	cdev->req->context = f_dfu;
 
-	s = getenv("serial#");
+	s = env_get("serial#");
 	if (s)
 		g_dnl_set_serialnumber((char *)s);
 
diff --git a/drivers/usb/gadget/f_fastboot.c b/drivers/usb/gadget/f_fastboot.c
index 7cd6d24..d05b74b 100644
--- a/drivers/usb/gadget/f_fastboot.c
+++ b/drivers/usb/gadget/f_fastboot.c
@@ -212,7 +212,7 @@
 		f->hs_descriptors = fb_hs_function;
 	}
 
-	s = getenv("serial#");
+	s = env_get("serial#");
 	if (s)
 		g_dnl_set_serialnumber((char *)s);
 
@@ -426,7 +426,7 @@
 		sprintf(str_num, "0x%08x", CONFIG_FASTBOOT_BUF_SIZE);
 		strncat(response, str_num, chars_left);
 	} else if (!strcmp_l1("serialno", cmd)) {
-		s = getenv("serial#");
+		s = env_get("serial#");
 		if (s)
 			strncat(response, s, chars_left);
 		else
@@ -441,7 +441,7 @@
 		}
 
 		sprintf(envstr, "fastboot.%s", cmd);
-		s = getenv(envstr);
+		s = env_get(envstr);
 		if (s) {
 			strncat(response, s, chars_left);
 		} else {
diff --git a/drivers/usb/host/ehci-fsl.c b/drivers/usb/host/ehci-fsl.c
index b57c6cd..62c431b 100644
--- a/drivers/usb/host/ehci-fsl.c
+++ b/drivers/usb/host/ehci-fsl.c
@@ -225,7 +225,7 @@
 				"phy_type", &len);
 #endif
 	else
-		phy_type = getenv("usb_phy_type");
+		phy_type = env_get("usb_phy_type");
 
 	if (!phy_type) {
 #ifdef CONFIG_SYS_FSL_USB_INTERNAL_UTMI_PHY