Change the SERIAL_AR933X Kconfig option from
'bool' to 'tristate' in order to allow to build
the driver as a module. Also extend the help text
of the option to reflect that.
Signed-off-by: NGabor Juhos <juhosg@openwrt.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>