mmc: mmci: Drop support for pdata GPIO numbers

All the machines using the MMCI are passing GPIOs for the
card detect and write protect using the device tree or
descriptor table (one single case, Integrator/AP IM-PD1).

Drop support for passing global GPIO numbers through
platform data, noone is using it.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>