[new uImage] Update naming convention for bootm/uImage related code

This patch introduces the following prefix convention for the
image format handling and bootm related code:

genimg_		- dual format shared code
image_		- legacy uImage format specific code
fit_		- new uImage format specific code
boot_		- booting process related code

Related routines are renamed and a few pieces of code are moved around and
re-grouped.

Signed-off-by: Marian Balakowicz <m8@semihalf.com>
diff --git a/board/siemens/common/fpga.c b/board/siemens/common/fpga.c
index a9a6dfe..48c1850 100644
--- a/board/siemens/common/fpga.c
+++ b/board/siemens/common/fpga.c
@@ -138,7 +138,7 @@
     int verify, i;
 
 #if defined(CONFIG_FIT)
-    if (gen_image_get_format ((void *)hdr) != IMAGE_FORMAT_LEGACY) {
+    if (genimg_get_format ((void *)hdr) != IMAGE_FORMAT_LEGACY) {
 	puts ("Non legacy image format not supported\n");
 	return -1;
     }
@@ -341,7 +341,7 @@
 
 	hdr = (image_header_t *)addr;
 #if defined(CONFIG_FIT)
-	if (gen_image_get_format ((void *)hdr) != IMAGE_FORMAT_LEGACY) {
+	if (genimg_get_format ((void *)hdr) != IMAGE_FORMAT_LEGACY) {
 	   puts ("Non legacy image format not supported\n");
 	   return -1;
 	}