mtd: msm_qpic_nand: fix issue with page read in MTD_OPS_RAW mode

When only last codeword is read from a page using MTD_OPS_RAW
mode, the QPIC_NAND_DEV0_CFG0 register is getting incorrectly
programmed for cw_per_page[8:6] field. This will result in
the incorrect CW sequence for the subsequent page reads and
thus read will return incorrect data.

Change-Id: Ic97c275ae6305af9280b4faa94a6be5fed20c6d6
Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>