mach-ux500: move keymaps to new file

Move keylayouts to a dedicated file and plug these keylayouts
for input platform data. This will make addition of new and custom
keylayouts localized.

Signed-off-by: Sundar Iyer <sundar.iyer@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>