rt2x00: Remove unneccessary internal Kconfig symbols.

CONFIG_RT2800PCI_PCI and CONFIG_RT2800PCI_SOC are strictly not needed
as we can check the dependent symbols directly in the rest of Kconfig
and the code, so clean up the Kconfig namespace a bit.

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