Input: add matrix keypad driver for Cirrus EP93xx

This is a keyboard driver for the Cirrus Logic EP93xx keypad matrix
peripheral. This driver is based on the pxa27x_keypad driver.

[dtor@mail.ru: Plug in input_dev->keycode so keymap can be changed
		from userspace.]
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>