mtd: msm_qpic_nand: Use flash device ECC capability for erase page

Page codeword's ECC data is used to determine if the page is actually
erased or not. On an erased page, this data is all 0xFF. The acceptable
bitflips on this ECC data is flash device dependent. So, always check
against flash device ECC capability value for erase page determination.

Change-Id: Ib3889f91c871b5f131fe8bc960ffa68ac11e0633
Signed-off-by: Pradeep P V K <ppvk@codeaurora.org>