mmc: sh_mmcif: fix late delayed work initialisation

If the driver is loaded with a card in the slot, mmc_add_host() will
schedule an immediate card-detection work, which will start IO and wait
for command completion. Usually the kernel first returns to the sh_mmcif
probe function, lets it finish and only then schedules the rescan work.
But sometimes, expecially under heavy system load, the work will be
scheduled immediately before returning to the probe method. In this case
it is important for the driver to be fully prepared for IO. For sh_mmcif
this means, that also the timeout work has to be initialised before
calling mmc_add_host(). It is also better to prepare interrupts
beforehand. Besides, since mmc_add_host() does card-detection itself,
there is no need to do it again immediately afterwards.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Chris Ball <cjb@laptop.org>