loop: Fix wrong masking of status flags

In faf1d25, loop_set_status() now assigns lo_status directly from
the passed in lo_flags, but then fixes it up by masking out flags that
can't be set by LOOP_SET_STATUS; unfortunately the mask was negated.

Re-ran all ltp ioctl_loop tests, and they all passed.

Pass run of the previously failing one:

tst_test.c:1247: INFO: Timeout per run is 0h 05m 00s
tst_device.c:88: INFO: Found free device 0 '/dev/loop0'
ioctl_loop01.c:49: PASS: /sys/block/loop0/loop/partscan = 0
ioctl_loop01.c:50: PASS: /sys/block/loop0/loop/autoclear = 0
ioctl_loop01.c:51: PASS: /sys/block/loop0/loop/backing_file =
'/tmp/ZRJ6H4/test.img'
ioctl_loop01.c:65: PASS: get expected lo_flag 12
ioctl_loop01.c:67: PASS: /sys/block/loop0/loop/partscan = 1
ioctl_loop01.c:68: PASS: /sys/block/loop0/loop/autoclear = 1
ioctl_loop01.c:77: PASS: access /dev/loop0p1 succeeds
ioctl_loop01.c:83: PASS: access /sys/block/loop0/loop0p1 succeeds

Summary:
passed   8
failed   0
skipped  0
warnings 0

Fixes: faf1d25 ("loop: Clean up LOOP_SET_STATUS lo_flags handling")
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Signed-off-by: Martijn Coenen <maco@android.com>
Tested-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/loop.c

@@ -1390,7 +1390,7 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
 		goto out_unfreeze;
 
 	/* Mask out flags that can't be set using LOOP_SET_STATUS. */
-	lo->lo_flags &= ~LOOP_SET_STATUS_SETTABLE_FLAGS;
+	lo->lo_flags &= LOOP_SET_STATUS_SETTABLE_FLAGS;
 	/* For those flags, use the previous values instead */
 	lo->lo_flags |= prev_lo_flags & ~LOOP_SET_STATUS_SETTABLE_FLAGS;
 	/* For flags that can't be cleared, use previous values too */