mm: remove unused arg of set_page_dirty_balance()

commit ed6d7c8e578331cad594ee70d60e2e146b5dce7b upstream.

There's only one caller of set_page_dirty_balance() and that will call it
with page_mkwrite == 0.

The page_mkwrite argument was unused since commit b827e496c893 "mm: close
page_mkwrite races".

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --cc include/linux/writeback.h
Simple merge

diff --cc mm/memory.c
Simple merge

diff --cc mm/page-writeback.c
Simple merge