scsi: st: fix kernel-doc mismatch

Fix kernel-doc function name and comments in st.c::read_ns_show():
change us to ns to match the function name.
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/st.c

@@ -4712,7 +4712,7 @@ static ssize_t read_byte_cnt_show(struct device *dev,
 static DEVICE_ATTR_RO(read_byte_cnt);
 
 /**
- * read_us_show - return read us - overall time spent waiting on reads in ns.
+ * read_ns_show - return read ns - overall time spent waiting on reads in ns.
  * @dev: struct device
  * @attr: attribute structure
  * @buf: buffer to return formatted data in