mmc: davinci: Poll status for small size transfers

For small size non-dma sdio transactions, it is sometimes better to poll
the mmc host and avoid interrupts altogether. Polling lowers the number
of interrupts and context switches. Tests have shown that for small
transactions, only a few polling iterations are needed, so this is worth
while.

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