Input: evdev - switch to bitmap API

Switch to bitmap API, i.e. bitmap_alloc(), bitmap_zalloc(), to show
clearly what we are allocating. Besides that it returns pointer of
bitmap type instead of opaque void *.

While here, replace memcpy() with bitmap_copy() for sake of consistency.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>