tmio_mmc: map SD control registers after enabling the MFD cell

ASIC3 can disable the memory, so we need to wait for mfd_cell->enable
to enable the memory before we can map the SD control registers.

Signed-off-by: Philipp Zabel <philipp.zabel@gmail.com>
Acked-by: Ian Molton <ian@mnementh.co.uk>
Signed-off-by: Pierre Ossman <pierre@ossman.eu>