prog_loading: add region_device representing memory

One can remove the struct buffer_area and use the region_device
embedded in the struct prog to represent the in-memory loaded
program. Do this by introducing a addrspace_32bit mem_region_device
that can have region_device operations performed on it. The
addrspace_32bit name was chosen to make it explicit that 32-bits
of address space is supported at the max.

Change-Id: Ifffa0ef301141de940e54581b5a7b6cd81311ead
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/10261
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Tested-by: build bot (Jenkins)

src/lib/prog_loaders.c

@@ -35,6 +35,9 @@
 #include <symbols.h>
 #include <timestamp.h>
 
+/* Only can represent up to 1 byte less than size_t. */
+const struct mem_region_device addrspace_32bit = MEM_REGION_DEV_INIT(0, ~0UL);
+
 #define DEFAULT_CBFS_LOADER_PRESENT \
 	(!ENV_VERSTAGE || (ENV_VERSTAGE && !CONFIG_RETURN_FROM_VERSTAGE))