s390/mm: Fix clearing storage keys for huge pages

s390/mm: Fix clearing storage keys for huge pages

The function __storage_key_init_range() expects the end address to be
the first byte outside the range to be initialized. I.e. end - start
should be the size of the area to be initialized.

The current code works because __storage_key_init_range() will still loop
over every page in the range, but it is slower than using sske_frame().

Fixes: 3afdfca69870 ("s390/mm: Clear skeys for newly mapped huge guest pmds")
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Link: https://lore.kernel.org/r/20240416114220.28489-3-imbrenda@linux.ibm.com
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>