Bump the valid GPIO range for rfkill up from 8 to 16.

AR5416 and later NICs have more than 8 (Well, more than 6) GPIO pins.
So to support rfkill on these NICs we need to bump this up or the
rfkill GPIO pin may get reset to the wrong value.

Noticed by: Anthony Jenkins <scoobi_doo@yahoo.com>


git-svn-id: svn+ssh://svn.freebsd.org/base/head@276150 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f