cbfs: alternative support for cbfs_load_payload()

In certain situations boot speed can be increased by providing an
alternative implementation to cbfs_load_payload(). The
ALT_CBFS_LOAD_PAYLOAD option allows for the mainboard or chipset to
provide its own implementation.

Booted baskingridge board with alternative and regular
cbfs_load_payload().

Change-Id: I547ac9881a82bacbdb3bbdf38088dfcc22fd0c2c
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/2782
Tested-by: build bot (Jenkins)
Reviewed-by: Marc Jones <marc.jones@se-eng.com>

src/lib/selfboot.c

@@ -536,4 +536,3 @@ int selfboot(struct lb_memory *mem, struct cbfs_payload *payload)
 out:
 	return 0;
 }
-