soc:qcom:dfc: change the default call bringup grant to 20k

In case of data call setup immediately after the power save disable,
the flow indications may get ignored, if the flow addition happens
after the indications are received.

This will block the initial address configuration procedure.
Having the default grant of 20K during flow addition, will avoid this
issue. Further flow indication's will keep parity between modem and
APPS with respect to grants.

Change-Id: Ib6264c6024a658e3de309ab7f52dd3d801114b8d
Signed-off-by: Sharath Chandra Vurukala <sharathv@codeaurora.org>