Input: ep93xx_keypad - update driver to new core support

This driver was merged before the ep93xx core support was added
for the keypad clock and acquiring/releasing the necessary gpio's.
Now that the proper support is in the ep93xx core this driver
needs to be updated to work correctly.

Summary of changes:
  1) Remove some unused members from the platform data.
  2) Remove the custom KEY macro and use the ones available in
     <linux/input/matrix_keypad.h>
  3) Remove the keypad_{readl/writel} macros and just use
     __raw_{readl/writel} directly.
  4) Update the clk_set_rate() call to work with the core support.
  5) Cleanup the probe routine and remove some unneeded messages.
  6) Use the ep93xx core functions to acquire and release the gpio's.
  7) Fix the clk_get() call to get the keypad clock.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>