misc: ocxl: use DEFINE_MUTEX() for mutex lock

mutex lock can be initialized automatically with DEFINE_MUTEX()
rather than explicitly calling mutex_init().
Acked-by: Frederic Barrat <fbarrat@linux.ibm.com>
Signed-off-by: Zheng Yongjun <zhengyongjun3@huawei.com>
Link: https://lore.kernel.org/r/20201224132446.31286-1-zhengyongjun3@huawei.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/ocxl/file.c

@@ -15,7 +15,7 @@
 
 static dev_t ocxl_dev;
 static struct class *ocxl_class;
-static struct mutex minors_idr_lock;
+static DEFINE_MUTEX(minors_idr_lock);
 static struct idr minors_idr;
 
 static struct ocxl_file_info *find_and_get_file_info(dev_t devno)
@@ -588,7 +588,6 @@ int ocxl_file_init(void)
 {
 	int rc;
 
-	mutex_init(&minors_idr_lock);
 	idr_init(&minors_idr);
 
 	rc = alloc_chrdev_region(&ocxl_dev, 0, OCXL_NUM_MINORS, "ocxl");