rtsx_usb_ms: Use msleep_interruptible() in polling loop

rtsx_usb_ms: Use msleep_interruptible() in polling loop

rtsx_usb_ms creates a task that mostly sleeps, but tasks in
uninterruptible sleep still contribute to the load average (for
bug-compatibility with Unix).  A load average of ~1 on a system that
should be idle is somewhat alarming.

Change the sleep to be interruptible, but still ignore signals.

A better fix might be to replace this loop with a delayed work item.

References: https://bugs.debian.org/765717
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Gbp-Pq: Topic bugfix/all
Gbp-Pq: Name rtsx_usb_ms-use-msleep_interruptible-in-polling-loop.patch