mtd: m25p80: add entry for w25q128

This device was reported over a year ago on OpenWrt mailing list in the
thread [OpenWrt-Devel] RedBoot partition table with winbond m25q128vb
(unfortunately, I can't find message id). Macpaul seemed to have
problems with partition driver, but it seems the device was working OK.

Reported-by: Macpaul Lin <macpaul@gmail.com>
Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>