ARM: S5P64X0: Move GPIO support files for merge S5P64X0

This patch moves S5P6440 GPIO support files from mach-s5p6440
into the new mach-s5p64x0 for merge S5P6440 and S5P6450 SocS.
NOTE: Not supported S5P6450 GPIO yet. Will be supported soon.

Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>