mfd: altera-sysmgr: Supply descriptions for 'np' and 'property' function args

Kerneldoc syntax is used, but not complete.  Arg descriptions are required.

Fixes the following W=1 build warnings:

 drivers/mfd/altera-sysmgr.c:95: warning: Function parameter or member 'np' not described in 'altr_sysmgr_regmap_lookup_by_phandle'
 drivers/mfd/altera-sysmgr.c:95: warning: Function parameter or member 'property' not described in 'altr_sysmgr_regmap_lookup_by_phandle'

Cc: Thor Thayer <thor.thayer@linux.intel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/mfd/altera-sysmgr.c

@@ -89,6 +89,9 @@ static struct regmap_config altr_sysmgr_regmap_cfg = {
  * altr_sysmgr_regmap_lookup_by_phandle
  * Find the sysmgr previous configured in probe() and return regmap property.
  * Return: regmap if found or error if not found.
+ *
+ * @np: Pointer to device's Device Tree node
+ * @property: Device Tree property name which references the sysmgr
  */
 struct regmap *altr_sysmgr_regmap_lookup_by_phandle(struct device_node *np,
 						    const char *property)