mtd: jedec_probe: fix LH28F640BF definition

Zaurus 5500 contains 2 LH28F640BFHE-PTTL90 (64M 4Mx16) and
the LH28F640BFHE-PTTL90.pdf datasheet available on the net shows
the exact erasesize and the OTP support.
At the moment only jedec_probe can discover the chip and
the NOR is mounted read only probably because of wrong vpp.

Signed-off-by: Andrea Adami <andrea.adami@gmail.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>