rt2x00: remove MCU requests for SoC platforms

The ralink SoC platforms do not have an MCU.

Signed-off-by: Luis Correia <luis.f.correia@gmail.com>
Acked-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: Gertjan van Wingerde <gwingerde@gmail.com>