fs/mpage.c: factor page_endio() out of mpage_end_io()

fs/mpage.c: factor page_endio() out of mpage_end_io()

page_endio() takes care of updating all the appropriate page flags once
I/O has finished to a page.  Switch to using mapping_set_error() instead
of setting AS_EIO directly; this will handle thin-provisioned devices
correctly.

Signed-off-by: Matthew Wilcox <[email protected]>
Cc: Dave Chinner <[email protected]>
Cc: Dheeraj Reddy <[email protected]>
Cc: Hugh Dickins <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>