mmc: omap_hsmmc: pass mmc_priv struct to gpio init / free

this is needed when installing callbacks in the host struct and not
in the platform data, e.g. cover detect irq should be stored in
omap_hsmmc_host and not platform data

Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Andreas Fenkart <afenkart@gmail.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>