x86: Initial commit for running as a coreboot payload

Add a target for running u-boot as a coreboot payload in boards.cfg, a
board, CPU and a config. This is a skeleton implementation which always
reports the size of memory as 64 MB.

Signed-off-by: Gabe Black <gabeblack@chromium.org>
diff --git a/boards.cfg b/boards.cfg
index 1e5b3e0..66c27a4 100644
--- a/boards.cfg
+++ b/boards.cfg
@@ -1007,6 +1007,7 @@
 gr_ep2s60                    sparc       leon3       -                   gaisler
 grsim                        sparc       leon3       -                   gaisler
 gr_xc3s_1500                 sparc       leon3       -                   gaisler
+coreboot-x86                 x86         x86        coreboot            chromebook-x86 coreboot    coreboot:SYS_TEXT_BASE=0xFC0000
 eNET                         x86         x86        eNET                -              sc520       eNET:SYS_TEXT_BASE=0x38040000
 eNET_SRAM                    x86         x86        eNET                -              sc520       eNET:SYS_TEXT_BASE=0x19000000
 # Target                     ARCH        CPU         Board name          Vendor	        SoC         Options