[ARM] pxa: fix incorrect PCMCIA PSKTSEL pin configuration for spitz

The original incorrect configuration caused GPIO79_nCS_3 being overriden,
thus resulted in the NAND flash not being detected. The real PSKTSEL pin
is on GPIO104 instead of GPIO79.

Signed-off-by: Eric Miao <eric.miao@marvell.com>
Cc: Richard Purdie <rpurdie@rpsys.net>