mmc: host: sdhci: don't set SDMA buffer boundary in ADMA mode

SDMA buffer boundary size parameter in block size register should only be
programmed if host controller DMA is operating in SDMA mode otherwise its
better not to set this parameter to avoid any side effect when DMA is
operating in ADMA mode operation.

Change-Id: Ia29ca4759ead2e4c9ea1d72908444a03bf205bac
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>