[RFKILL]: Add rfkill documentation
[RFKILL]: Add rfkill documentation

Add a documentation file which contains
a short description about rfkill with some
notes about drivers and the userspace interface.

Changes since v1 and v2:
 - Spellchecking

Signed-off-by: Ivo van Doorn <eb95d5f7a69eb0f8d26a960fe33483acdf581277@gmail.com>
Acked-by: Dmitry Torokhov <10a8c465cefc9bdd6c925e26964d23c90f1141cc@mail.ru>
Acked-by: Randy Dunlap <e1d10faa7e2a0c027bf1ff1d20e7fd10154be7ea@oracle.com>

TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas