staging: greybus: uart: fix TIOCSSERIAL jiffies conversions

The port close_delay and closing_wait parameters set by TIOCSSERIAL are
specified in jiffies and not milliseconds.

Add the missing conversions so that TIOCSSERIAL works as expected also
when HZ is not 1000.

Fixes: e68453ed ("greybus: uart-gb: now builds, more framework added")
Cc: stable@vger.kernel.org	# 4.9
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20210407102334.32361-6-johan@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>