arm: Refactor bootm to reduce #ifdefs

With fewer #ifdefs the code is more readable and more of the code is
compiled for all boards. Add defines in the header file to control
what features are enabled, and then use if() instead of #ifdef.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/common/cmd_bootm.c b/common/cmd_bootm.c
index b9b2979..dd6cafa 100644
--- a/common/cmd_bootm.c
+++ b/common/cmd_bootm.c
@@ -276,7 +276,7 @@
 #if defined(CONFIG_FIT)
 	} else if (images.fit_uname_os) {
 		ret = fit_image_get_entry(images.fit_hdr_os,
-				images.fit_noffset_os, &images.ep);
+					  images.fit_noffset_os, &images.ep);
 		if (ret) {
 			puts("Can't get entry point property!\n");
 			return 1;