commonlib/region: Turn addrspace_32bit into a more official API

We had the addrspace_32bit rdev in prog_loaders.c for a while to help
represent memory ranges as an rdev, and we've found it useful for a
couple of things that have nothing to do with program loading. This
patch moves the concept straight into commonlib/region.c so it is no
longer anchored in such a weird place, and easier to use in unit tests.
Also expand the concept to the whole address space (there's no real need
to restrict it to 32 bits in 64-bit environments) and introduce an
rdev_chain_mem() helper function to make it a bit easier to use. Replace
some direct uses of struct mem_region_device with this new API where it
seems to make sense.

Signed-off-by: Julius Werner <jwerner@chromium.org>
Change-Id: Ie4c763b77f77d227768556a9528681d771a08dca
Reviewed-on: https://review.coreboot.org/c/coreboot/+/52533
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/lib/prog_loaders.c

@@ -16,10 +16,6 @@
 #include <timestamp.h>
 #include <security/vboot/vboot_common.h>
 
-/* Only can represent up to 1 byte less than size_t. */
-const struct mem_region_device addrspace_32bit =
-	MEM_REGION_DEV_RO_INIT(0, ~0UL);
-
 void run_romstage(void)
 {
 	struct prog romstage =