input: davinci_keyscan: remove unnecessary includes

The mach/ and asm/ includes are not needed in davinci_keyscan, but they
will cause build problems once we make mach/irqs.h a private header for
mach-davinci.

Remove all unused header includes.

Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>