Some backends call hvc_kick() to wakeup the HVC thread from its
slumber upon incoming characters. This however doesn't work
properly because it uses msleep_interruptible() which is mostly
immune to wake_up_process(). It will basically go back to sleep
until the timeout is expired (only signals can really wake it).

Replace it with a simple shedule_timeout_interruptible() instead,
which may wakeup earlier every now and then but we really don't
care in this case.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>