ARM: S3C64XX: Remove gpio-bank-X header files

The gpio-bank-X header files of S3C64XX have definitions
which can be substituted by other common GPIO API.

Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>