dax: remove redundant assignment to variable rc

The variable rc is being assigned an value and then is being re-assigned
a new value in the next statement. The assignment is redundant and can
be removed.

Cleans up clang scan build warning:
drivers/dax/bus.c:1207:2: warning: Value stored to 'rc' is never
read [deadcode.DeadStores]

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Vishal Verma <vishal.l.verma@intel.com>
Link: https://lore.kernel.org/r/20240415101928.484143-1-colin.i.king@gmail.com
Signed-off-by: Ira Weiny <ira.weiny@intel.com>

Author: ColinIanKing

drivers/dax/bus.c

@@ -1204,7 +1204,6 @@ static ssize_t mapping_store(struct device *dev, struct device_attribute *attr,
 	if (rc)
 		return rc;
 
-	rc = -ENXIO;
 	rc = down_write_killable(&dax_region_rwsem);
 	if (rc)
 		return rc;