[SPARC]: sbus/envctrl: replace schedule_timeout() with msleep_interruptible()

Use msleep_interruptible() instead of schedule_timeout() to guarantee
the task delays as expected. Change the units of poll_interval to
msecs as it is only used in this delay.

Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>
Signed-off-by: Domen Puncer <domen@coderock.org>
Signed-off-by: David S. Miller <davem@davemloft.net>