staging: serqt_usb2: remove retval initialisation in qt_tiocmget and qt_tiocmset

in qt_tiocmset,

the retval gets assigned if we have a valid serial pointer in the critical section
(between mutex_lock and _unlock) of the code, no need to initialise this variable.

the same retval assignment follows in the qt_tiocmget function also, so remove the
initialisation here too.

Signed-off-by: Devendra Naga <develkernel412222@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>