serial: msm_geni_serial: Add support for active pinctrl state

This change helps configuring GPIO to non UART function which makes
them to stay low when not in use. Kernel framework considers default
state to configure GPIOs during probe.

Adding active pinctrl node for the active configuration set and current
default configuration will be used during the probe time.

Change-Id: I082a1b4c3e42ca5b6005fd038a011e6b054b25b5
Signed-off-by: Mitul Golani <mgolani@codeaurora.org>