libpayload: Add get_option_from()

This function allows reading the nvram configuration table from
locations other than the cbtable.

Change-Id: I56c9973a9ea45ad7bf0185b70d11c9ce5d0e0e1b
Signed-off-by: Patrick Georgi <patrick.georgi@secunet.com>
Reviewed-on: http://review.coreboot.org/213
Tested-by: build bot (Jenkins)
Reviewed-by: Marc Jones <marcj303@gmail.com>

payloads/libpayload/include/libpayload.h

@@ -194,6 +194,7 @@ void video_console_set_cursor(unsigned int cursorx, unsigned int cursory);
 
 /* drivers/option.c */
 void fix_options_checksum(void);
+int get_option_from(struct cb_cmos_option_table *option_table, void *dest, char *name);
 int get_option(void *dest, char *name);
 
 /**