Fix CMOS handling for non-USE_OPTION_TABLE configuration

Fix CMOS handling for non-USE_OPTION_TABLE configuration

The read_option macro still emitted CMOS_VSTART_*/CMOS_VEND_* symbols,
which fail without an option table (as no option_table.h defines them).

Discard them by using a macro instead of a static inline function.

Change-Id: I8d001f971681277a344b6788725746491546b607
Signed-off-by: Patrick Georgi <patrick.georgi@secunet.com>
Reviewed-on: http://review.coreboot.org/442
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>