loaders: add program_loading.h header file

Instead of two headers for payload and ramstage loading
combine the 2 files into one. This also allows for easier
refactoring by keeping header files consistent.

Change-Id: I4a6dffb78ad84c78e6e96c886d361413f9b4a17d
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/8708
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/lib/selfboot.c

@@ -27,7 +27,7 @@
 #include <cbfs.h>
 #include <lib.h>
 #include <bootmem.h>
-#include <payload_loader.h>
+#include <program_loading.h>
 
 /* from ramstage.ld: */
 extern unsigned char _ram_seg;