mtd: msm_qpic_nand: Fix buffer overflow issue

Correct the size argument passed to memset() in function
msm_nand_block_isbad() to fix buffer overflow issue.

CRs-fixed: 561236
Change-Id: I1c664ef529a42901d1f3d5d1d7b747cf58f886b6
Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>