MIPS: JZ4770: Detach MSC platform data from platform code

The platform code didn't need the actual data inside the struct, but
it still depended on the header. That dependency was removed and the
header is no longer included by the platform code.
mmc: JZ4770: Renamed platform data header

The header contains only the platform data struct definition at this
point, so renamed it to set it apart from the other headers that still
contain register definitions as well.

When migrating to Linux 3.10, this header should become part of the
JZ4770 MMC driver, while currently it is introduced as part of the
platform.
mmc: JZ4770: Customize GPIO pins using data instead of callbacks

Used an approach similar to the JZ4740 driver. The platform data
describes which GPIO pins are used and whether they are high or low
active, the driver will then manage those pins.
MIPS: JZ4770: GCW0: Update handling of MMC GPIO pins

See "Customize GPIO pins using data instead of callbacks" commit on the
JZ4770 MMC driver.
MIPS: JZ4770: Removed MMC GPIO function setting macros

See "Customize GPIO pins using data instead of callbacks" commit on the
MMC driver.