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/board/gdsys/a38x/keyprogram.c b/board/gdsys/a38x/keyprogram.c
index a4a6f1c..d75e08b 100644
--- a/board/gdsys/a38x/keyprogram.c
+++ b/board/gdsys/a38x/keyprogram.c
@@ -129,12 +129,12 @@
 	char *hexprog;
 	struct key_program *prog;
 
-	cmd = getenv("loadkeyprogram");
+	cmd = env_get("loadkeyprogram");
 
 	if (!cmd || run_command(cmd, 0))
 		return 1;
 
-	hexprog = getenv("keyprogram");
+	hexprog = env_get("keyprogram");
 
 	if (decode_hexstr(hexprog, &binprog))
 		return 1;
diff --git a/board/gdsys/mpc8308/hrcon.c b/board/gdsys/mpc8308/hrcon.c
index c6566e9..7e48507 100644
--- a/board/gdsys/mpc8308/hrcon.c
+++ b/board/gdsys/mpc8308/hrcon.c
@@ -103,7 +103,7 @@
 
 int checkboard(void)
 {
-	char *s = getenv("serial#");
+	char *s = env_get("serial#");
 	bool hw_type_cat = pca9698_get_value(0x20, 20);
 
 	puts("Board: ");
diff --git a/board/gdsys/mpc8308/strider.c b/board/gdsys/mpc8308/strider.c
index 34e9d19..fec6915 100644
--- a/board/gdsys/mpc8308/strider.c
+++ b/board/gdsys/mpc8308/strider.c
@@ -106,7 +106,7 @@
 
 int checkboard(void)
 {
-	char *s = getenv("serial#");
+	char *s = env_get("serial#");
 	bool hw_type_cat = pca9698_get_value(0x20, 18);
 
 	puts("Board: ");
diff --git a/board/gdsys/p1022/controlcenterd-id.c b/board/gdsys/p1022/controlcenterd-id.c
index 95f11fb..61c030a 100644
--- a/board/gdsys/p1022/controlcenterd-id.c
+++ b/board/gdsys/p1022/controlcenterd-id.c
@@ -1043,13 +1043,13 @@
 		goto failure;
 
 	/* run "prepboot" from env to get "mmcdev" set */
-	cptr = getenv("prepboot");
+	cptr = env_get("prepboot");
 	if (cptr && !run_command(cptr, 0))
-		mmcdev = getenv("mmcdev");
+		mmcdev = env_get("mmcdev");
 	if (!mmcdev)
 		goto failure;
 
-	cptr = getenv("ramdiskimage");
+	cptr = env_get("ramdiskimage");
 	if (cptr)
 		image_path = cptr;
 
diff --git a/board/gdsys/p1022/controlcenterd.c b/board/gdsys/p1022/controlcenterd.c
index 01064dc..24e58cb 100644
--- a/board/gdsys/p1022/controlcenterd.c
+++ b/board/gdsys/p1022/controlcenterd.c
@@ -223,7 +223,7 @@
 #ifdef CONFIG_TRAILBLAZER
 int do_bootd(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
-	return run_command(getenv("bootcmd"), flag);
+	return run_command(env_get("bootcmd"), flag);
 }
 
 int board_early_init_r(void)