mtd: msm_qpic_nand: Adjustment of reg offsets from the devicetree

Certain QPIC core registers address offsets have changed between
chipsets while the base of the register control regions remain the
same. Add a new property qcom,reg_adjustment_offset to allow adjustment
of the offset from the devicetree nodes.

Change-Id: Ic858c12543227a00a52e2000300fabe7a4423de8
Signed-off-by: Nikhilesh Reddy <reddyn@codeaurora.org>