mmc: s3cmci: moved mach/regs-sdi.h into s3cmci device driver

Since mach/regs-sdi.h is used only for s3cmci.c, so this moves the
header file into the driver file, drivers/mmc/host/s3cmci.c file.

Cc: Chris Ball <cjb@laptop.org>
Tested-by: Sylwester Nawrocki <sylvester.nawrocki@gmail.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>