sf: Macronix additional chips supported

new chips supported:-
MX25L1605D, MX25L3205D, MX25L6405D, MX25L12855E
out of which MX25L6405D and MX25L12855E tested on Kirkwood platforms

Modified the Macronix flash support to use 2 bytes of device id instead of 1
This was required to support MX25L12855E

Signed-off-by: Piyush Shah <spiyush@marvell.com>
Signed-off-by: Prafulla Wadaskar <prafulla@marvell.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>