rdc321x: GPIO routines bugfixes

This patch fixes the use of GPIO routines which are in the PCI
configuration space of the RDC321x, therefore reading/writing
to this space without spinlock protection can be problematic.

We also now request and free GPIOs and support the MGB100
board, previous code was very AR525W-centric.

Signed-off-by: Volker Weiss <volker@tintuc.de>
Signed-off-by: Florian Fainelli <florian.fainelli@telecomint.eu>
Signed-off-by: Ingo Molnar <mingo@elte.hu>