DAC960: remove sleep_on usage

sleep_on and its variants are going away. The use of sleep_on() in
DAC960_V2_ExecuteUserCommand seems to be bogus because the command
by the time we get there, the command has completed already and
we just enter the timeout. Based on this interpretation, I concluded
that we can replace it with a simple msleep(1000) and rearrange the
code around it slightly.

The interruptible_sleep_on_timeout in DAC960_gam_ioctl seems equivalent
to the race-free version using wait_event_interruptible_timeout.
I left the driver to return -EINTR rather than -ERESTARTSYS to preserve
the timeout behavior.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Jens Axboe <axboe@fb.com>