mtd: msm_qpic_nand: Workaround to get the correct density for JSC part

The 8 x 8 JSC MCP part has 2 x 4Gbit NAND dies from Hynyx and
supports ONFI. But ONFI parameter page field values below read from the
device only account for 4Gbit instead of 8Gbit:

Pages/Block : 64
Page size  : 4096
num_blocks_per_unit : 2048
num_units : 1

JSC vendor has no plans to “correct” the ONFI parameter page
field values in their current and future 8 x 8 MCP parts to properly
identify the NAND device size as 8Gbit.

Using Read ID values (manufacture ID (0xAD), device ID(0xA3)) instead to
identify the part and multiplying the density to identify the part as
8Gbit device size.

Change-Id: Id900f3475e68740597fbc4e6decb1b7920f09c57
Signed-off-by: Sarthak Garg <sartgarg@codeaurora.org>