omap_gpmc: Take omap_mpu_state* in omap_gpmc_init

omap_gpmc: Take omap_mpu_state* in omap_gpmc_init

Take a pointer to the omap mpu state struct in omap_gpmc_init.
Some details of GPMC behaviour depend on the OMAP version we
are a part of.

Signed-off-by: Juha Riihimäki <juha.riihimaki@nokia.com>
[Riku Voipio: Fixes and restructuring patchset]
Signed-off-by: Riku Voipio <riku.voipio@iki.fi>
[Peter Maydell: More fixes and cleanups for upstream submission]
Signed-off-by:  Peter Maydell <peter.maydell@linaro.org>