msm-geni-serial: Correct the interrupt polling logic in uart

Correct the interrupt polling logic in uart and depend on the
interrupt routine instead of polling where ever possible.

Change-Id: I7a2a8164d2dabf74755305a9c34a45e0eaec425d
Signed-off-by: Prudhvi Yarlagadda <pyarlaga@codeaurora.org>
Signed-off-by: Venkata Manasa Kakarla <venkka@codeaurora.org>