msm_serial: Fix the timing requirement for UIMs

Some commercial SIMS require a longer stop bit. This change
makes the driver confirm to the standard.

Change-Id: I270a101213d7dd31acf2608786541e3f11e2f2b8
Acked-by: Kaushik Sikdar <ksikdar@qualcomm.com>
Signed-off-by: Rohit Vaswani <rvaswani@codeaurora.org>