mmc: omap_hsmmc: remove prepare/complete system suspend support.

The only function of these 'prepare' and 'complete' is to
disable the 'card detect' irq during suspend.

The commit which added this,
commit a48ce884
    mmc: omap_hsmmc: Introduce omap_hsmmc_prepare/complete

justified it by the need to avoid the registration of new devices
during suspend.
However mmc_pm_notify will set ->rescan_disable in the 'prepare'
stage and clear it in the 'complete' stage, so no card detection
will actually happen.
Also the interrupt will be disabled before final suspend as part
of common suspend processing.

So this disabling of the interrupt is unnecessary, and interferes
with a transition to using common code for card-detect management.

Cc: Felipe Balbi <balbi@ti.com>
Cc: Venkatraman S <svenkatr@ti.com>
Cc: Chris Ball <cjb@laptop.org>
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>