ath6kl: remove completely pointles platform driver

Perhaps there was some good intention on having some platform
driver on ath6kl, but right now its pointless. Kill!

Cc: Naveen Singh <nsingh@atheros.com>
Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>