s390/mm: fixing comment so that parameter name match

Signed-off-by: Dominik Dingel <[e-mail]>
Signed-off-by: Martin Schwidefsky <[e-mail]>

arch/s390/mm/pgtable.c

···
 /**
  * gmap_ipte_notify - mark a range of ptes for invalidation notification
  * @gmap: pointer to guest mapping meta data structure
- * @address: virtual address in the guest address space
+ * @start: virtual address in the guest address space
  * @len: size of area
  *
  * Returns 0 if for each page in the given range a gmap mapping exists and