bootm: refactor image detection and os load steps

Created a bootm_start() that handles the parsing and detection of all
the images that will be used by the bootm command (OS, ramdisk, fdt).
As part of this we now tract all the relevant image offsets in the
bootm_headers_t struct. This will allow us to have all the needed
state for future sub-commands and lets us reduce a bit of arch
specific code on SPARC.

Created a bootm_load_os() that deals with decompression and loading
the OS image.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
diff --git a/include/image.h b/include/image.h
index c1acd7b..9be806e 100644
--- a/include/image.h
+++ b/include/image.h
@@ -187,6 +187,13 @@
 	uint8_t		ih_name[IH_NMLEN];	/* Image Name		*/
 } image_header_t;
 
+typedef struct image_info {
+	ulong		start, end;		/* start/end of blob */
+	ulong		image_start, image_len; /* start of image within blob, len of image */
+	ulong		load;			/* load addr for the image */
+	uint8_t		comp, type, os;		/* compression, type of image, os type */
+} image_info_t;
+
 /*
  * Legacy and FIT format headers used by do_bootm() and do_bootm_<os>()
  * routines.
@@ -219,6 +226,7 @@
 #endif
 #endif
 
+	image_info_t	os;		/* os image info */
 	ulong		ep;		/* entry point of OS */
 
 	ulong		rd_start, rd_end;/* ramdisk start/end */
@@ -229,6 +237,7 @@
 	ulong		ft_len;		/* length of flat device tree */
 
 	int		verify;		/* getenv("verify")[0] != 'n' */
+	int		valid;		/* set to 1 if we've set values in the header */
 #ifndef USE_HOSTCC
 	struct lmb	lmb;		/* for memory mgmt */
 #endif