mmc: omap_hsmmc: Workaround for errata id i802

According to errata i802, DCRC error interrupts
(MMCHS_STAT[21] DCRC=0x1) can occur during the tuning procedure.

The DCRC interrupt, occurs when the last tuning block fails
(the last ratio tested). The delay from CRC check until the
interrupt is asserted is bigger than the delay until assertion
of the tuning end flag. Assertion of tuning end flag is what
masks the interrupts. Because of this race, an erroneous DCRC
interrupt occurs.

The suggested  workaround is to disable DCRC interrupts during
the tuning procedure which is implemented here.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>