serial:msm_geni_serial: Handling the cts counter in uart driver

Handle the CTS counter whenever the change in CTS interrupt occur.
Using the M_IO_DATA_ASSERT bit in interrupt register, this will get
set when CTS is high.

Change-Id: I43c629f4d026af4a7e82d0d6d01b826259b0b1b5
Signed-off-by: Venkata Manasa Kakarla <venkka@codeaurora.org>