mfd: Return twl6030_mmc_card_detect IRQ for board setup

Card detect IRQ from the TWL6030 used to be provided to the MMC
controller code using a statically allocated IRQ scheme:

  card_detect_irq = TWL6030_IRQ_BASE + MMCDETECT_INTR_OFFSET;

This is no longer valid in a SPARSE_IRQ context since there is no more
pre-defined TWL6030_IRQ_BASE.

Return the proper card detect IRQ value in the twl6030_mmc_card_detect_config
that will be called from the MMC controller.

Signed-off-by: Benoit Cousson <b-cousson@ti.com>
Cc: Felipe Balbi <balbi@ti.com>
Cc: Tony Lindgren <tony@atomide.com>
Cc: Rajendra Nayak <rnayak@ti.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>