mmc: sdhci-msm: configure adma descriptors for large request size

This patch adds a function to configure adma descriptors to
support request size upto 512MB.

Change-Id: Ie2ad32106422bb5bdbf72b08d1ecdd74d9a93c19
Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
[xiaonian@codeaurora.org: fix trivial merge conflict]
Signed-off-by: Xiaonian Wang <xiaonian@codeaurora.org>