ocxl: Fix missing unlock on error in afu_ioctl_enable_p9_wait()

Add the missing unlock before return from function
afu_ioctl_enable_p9_wait() in the error handling case.

Fixes: e948e06fc63a ("ocxl: Expose the thread_id needed for wait on POWER9")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Reviewed-by: Alastair D'Silva <alastair@d-silva.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

drivers/misc/ocxl/file.c

@@ -139,8 +139,10 @@ static long afu_ioctl_enable_p9_wait(struct ocxl_context *ctx,
 		// Locks both status & tidr
 		mutex_lock(&ctx->status_mutex);
 		if (!ctx->tidr) {
-			if (set_thread_tidr(current))
+			if (set_thread_tidr(current)) {
+				mutex_unlock(&ctx->status_mutex);
 				return -ENOENT;
+			}
 
 			ctx->tidr = current->thread.tidr;
 		}