coreboot: introduce notion of bootmem for memory map at boot

The write_coreboot_table() in coreboot_table.c was already using
struct memrange for managing and building up the entries that
eventually go into the lb_memory table. Abstract that concept
out to a bootmem memory map. The bootmem concept can then be
used as a basis for loading payloads, for example.

Change-Id: I7edbbca6bbd0568f658fde39ca93b126cab88367
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/5302
Tested-by: build bot (Jenkins)
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>

src/lib/Makefile.inc

@@ -63,6 +63,7 @@ romstage-$(CONFIG_ARCH_X86) += gcc.c
 ramstage-y += hardwaremain.c
 ramstage-y += selfboot.c
 ramstage-y += coreboot_table.c
+ramstage-y += bootmem.c
 ifneq ($(CONFIG_HAVE_ARCH_MEMSET),y)
 ramstage-y += memset.c
 endif