mmc: dw_mmc: Support SDIO interrupts for all slots

The Patch adds the support for SDIO interrupts for all slots.
It includes enabling of SDIO interrupts through dw_mci_enable_sdio_irq
and the handling of the slot specific interrupts in the Interrupt Service
Routine.

Signed-off-by: Shashidhar Hiremath <shashidharh@vayavyalabs.com>
Acked-by: James Hogan <james.hogan@imgtec.com>
Signed-off-by: Chris Ball <cjb@laptop.org>