mmc: sdhci-msm: add quirk for max_discard calculation

The SDHCi driver by default specifies a parameter that causes the
core layer to calculate a max discard value which will be set on the
mmc queue. Unfortunately the value calculated because of this would
be very small compared to what comes in by default. As a result of
this, any secure discard kind of operations are very slow.

Instead add quirk so that any SDHCi hosts that would like to use
the default value can do so.

Change-Id: Ifa1343c3e7f14b031da30b06203a8831ba544889
Signed-off-by: Krishna Konda <kkonda@codeaurora.org>