rt2x00: Fix build error when crypto support is disabled

When only rt2400pci or rt2500pci is compiled without any of the other
rt2x00 modules, then CONFIG_RT2X00_LIB_CRYPTO will not be enabled.

However rt2x00mac_set_tim() implemented within #ifdef CONFIG_RT2X00_LIB_CRYPTO
statements while the declaration is placed outside the definition. This results in linking
errors as reporte by Ken.

rt2x00_set_tim() has nothing to do with crypto, and thus should be moved outside
of the #ifdef statements.

Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>