gpio: s3c: Fix the GPIO driver

gpio: s3c: Fix the GPIO driver

The GPIO driver didn't correctly compute the bank offset
from the GPIO number and caused random writes into the
GPIO block address space. Fix the driver so it actually
does the writes correctly. While at it, make use of the
clrsetbits_le32() mechanisms.

Signed-off-by: Marek Vasut <[email protected]>
Cc: Kyungmin Park <[email protected]>
Cc: Lukasz Majewski <[email protected]>
Cc: Minkyu Kang <[email protected]>
Cc: Vladimir Zapolskiy <[email protected]>
Signed-off-by: Minkyu Kang <[email protected]>