tty: serial: qcom_geni_serial: Rectify UART suspend mechanism

UART driver checks for the PM state and denies suspend if state is ACTIVE.
This makes UART to deny suspend when client keeps port open which is not
correct. Instead follow framework and obey suspend-resume callbacks.

Signed-off-by: Mukesh Kumar Savaliya <msavaliy@codeaurora.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>