Add nobh_wripage() support for the filesystems which uses
nobh_prepare_write/nobh_commit_write().

Idea here is to reduce unnecessary bufferhead creation/attachment to the
page through pageout()->block_write_full_page().  nobh_wripage() tries to
operate by directly creating bios, but it falls back to
__block_write_full_page() if it can't make progress.

Note that this is not really generic routine and can't be used for
filesystems which uses page->Private for anything other than buffer heads.
Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>