io_uring: remove unneeded variable 'ret'

Fix the following coccicheck warning:
./fs/io_uring.c:8984:5-8: Unneeded variable: "ret". Return "0" on line
8998
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Link: https://lore.kernel.org/r/1615271441-33649-1-git-send-email-yang.lee@linux.alibaba.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -9022,7 +9022,6 @@ static unsigned long io_uring_nommu_get_unmapped_area(struct file *file,
 
 static int io_sqpoll_wait_sq(struct io_ring_ctx *ctx)
 {
-	int ret = 0;
 	DEFINE_WAIT(wait);
 
 	do {
@@ -9036,7 +9035,7 @@ static int io_sqpoll_wait_sq(struct io_ring_ctx *ctx)
 	} while (!signal_pending(current));
 
 	finish_wait(&ctx->sqo_sq_wait, &wait);
-	return ret;
+	return 0;
 }
 
 static int io_get_ext_arg(unsigned flags, const void __user *argp, size_t *argsz,