ARM: pxa168: correct nand pmu setting

The original pair of <0x01db, 208000000> is invalid. Correct it to
the valid value.

The 6th bit of the NFC APMU register indicates NFC works whether
at 156Mhz or 78Mhz. So 0x19b indicates NFC works at 156Mhz, and
0x1db indicates it works at 78Mhz.

Signed-off-by: Lei Wen <leiwen@marvell.com>
Cc: stable@kernel.org
Signed-off-by: Eric Miao <eric.y.miao@gmail.com>