[coreboot] Patch merged into coreboot/master: 7b69454 libpayload: only compile drivers/serial.c on machines that use it.

the following patch was just integrated into master:
commit 7b6945405a7c703bb371cab973238e0c15b07cdf
Author: Ronald G. Minnich 
Date:   Fri Feb 15 08:13:29 2013 -0800

libpayload: only compile drivers/serial.c on machines that use it.

Create a new serial console variable, X86_SERIAL_CONSOLE
    which is only enabled when SERIAL_CONSOLE and ARCH_X86 are defined.

Builds for x86 and ARM.

Change-Id: I607253c418de015975a839e3c33577842885ec0c
    Signed-off-by: Ronald G. Minnich 
    Reviewed-on: http://review.coreboot.org/2412
    Tested-by: build bot (Jenkins)
    Reviewed-by: Gabe Black

Build-Tested: build bot (Jenkins) at Fri Feb 15 17:22:38 2013, giving +1
Reviewed-By: Gabe Black  at Sat Feb 16 04:48:50 2013, giving +2
See http://review.coreboot.org/2412 for details.

-gerrit