mmc: davinci: Eliminate spurious interrupts

The davinci mmc interrupt handler fills the fifo, as long as the DXRDY
or DRRDY bits are set in the status register.

If interrupts fire during this loop, they will be handled by the
handler, but the interrupt controller will still buffer these. As a
result, the handler will be called again to serve these needlessly. In
order to avoid these spurious interrupts, keep interrupts masked while
filling the fifo.

Signed-off-by: Ido Yariv <ido@wizery.com>
Tested-by: Rajashekhara, Sudhakar <sudhakar.raj@ti.com>
Signed-off-by: Chris Ball <cjb@laptop.org>