[media] rc/keymaps: Use KEY_LEFTMETA were pertinent

Using xev and testing the "Windows" key on a normal keyboard, it
is mapped as KEY_LEFTMETA. So, as this is the standard code for
it, use it, instead of a generic, meaningless KEY_PROG1.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Signed-off-by: Jarod Wilson <jarod@redhat.com>