mmc: sdhci-msm: avoid using NOP ADMA descriptor for EOT

Qualcomm SDCC doesn't need NOP descriptor for End of
transfer (EOT).
This change insure that no NOP descriptor will be sent
in order to notify EOT, instead, the EOT will be marked for
the last descriptor.

Change-Id: Ia670bc901af2196a415c2aa54357704949a7b112
Signed-off-by: Talel Shenhar <tatias@codeaurora.org>