mtd: msm_nand: Support for partial page read and multi page write

Linux UBI (Unsorted Block Images) driver is a volume management system
for raw flash devices. It makes use of MTD character device interface,
and it allows having UBIFS (UBI filesystem) on top of it.

The current msm nand driver doesn't support partial page read
and multi page write of vmalloc'ed data buffer which is needed by
UBI driver. Add support for these in low level nand driver.

Change-Id: Ibe47116b1b8c9e58f8703f62710ff5926eb8b6dc
Acked-by: Ho Lee <holee@qualcomm.com>
Signed-off-by: Sujit Reddy Thumma <sthumma@codeaurora.org>