VM: make zap_page_range() return void

... since all callers ignore its return value and it's been
useless since commit 97a894136f29802da19a15541de3c019e1ca147e
(mm: Remove i_mmap_lock lockbreak) anyway.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2 files changed