mtd: msm_qpic_nand: refactor code for optimizations

Refactor the code in order to prepare for upcoming chagnes
that focus on improving read/write perforamnce of the nand
controller.

Change-Id: If38fc7bc288466f11df814480669914573641b61
Signed-off-by: Krishna Konda <kkonda@codeaurora.org>