usb: USB download gadget and functions config options coherent naming

This introduces a coherent scheme for naming USB download gadget and functions
config options. The download USB gadget config option is moved to
CONFIG_USB_GADGET_DOWNLOAD for better consistency with other gadgets and each
function's config option is moved to a CONFIG_USB_FUNCTION_ prefix.

Signed-off-by: Paul Kocialkowski <contact@paulk.fr>
Tested-by: Lukasz Majewski <l.majewski@samsung.com>

Test HW: Odroid_XU3 (Exynos5422), trats (Exynos4210)
diff --git a/board/samsung/common/Makefile b/board/samsung/common/Makefile
index 93347ef..5fb01ce 100644
--- a/board/samsung/common/Makefile
+++ b/board/samsung/common/Makefile
@@ -6,7 +6,7 @@
 #
 
 obj-$(CONFIG_SOFT_I2C_MULTI_BUS) += multi_i2c.o
-obj-$(CONFIG_USBDOWNLOAD_GADGET) += gadget.o
+obj-$(CONFIG_USB_GADGET_DOWNLOAD) += gadget.o
 obj-$(CONFIG_MISC_COMMON) += misc.o
 
 ifndef CONFIG_SPL_BUILD
diff --git a/board/siemens/common/factoryset.c b/board/siemens/common/factoryset.c
index d81f548..6c869ed 100644
--- a/board/siemens/common/factoryset.c
+++ b/board/siemens/common/factoryset.c
@@ -144,7 +144,7 @@
 	unsigned char eeprom_buf[0x3c00], hdr[4], buf[MAX_STRING_LENGTH];
 	unsigned char *cp, *cp1;
 
-#if defined(CONFIG_DFU_FUNCTION)
+#if defined(CONFIG_USB_FUNCTION_DFU)
 	factory_dat.usb_vendor_id = CONFIG_G_DNL_VENDOR_NUM;
 	factory_dat.usb_product_id = CONFIG_G_DNL_PRODUCT_NUM;
 #endif
@@ -202,7 +202,7 @@
 		cp1 += 3;
 	}
 
-#if defined(CONFIG_DFU_FUNCTION)
+#if defined(CONFIG_USB_FUNCTION_DFU)
 	/* read vid and pid for dfu mode */
 	if (0 <= get_factory_record_val(cp, size, (uchar *)"USBD1",
 					(uchar *)"vid", buf,