[ARM] S3C: Fix PWM build on S3C6400

The pwm-clock.c needs <mach/map.h> which is included
via other means on S3C24XX systems, so ensure it is
explicitly included.

Remove the includes of regs-clock.h and regs-gpio.h as
these are not needed by the build.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>