Squashfs: Use vmalloc rather than kmalloc for zlib workspace

Squashfs: Use vmalloc rather than kmalloc for zlib workspace

BugLink: http://bugs.launchpad.net/bugs/761134

commit 117a91e0f25fd7698e20ac3dfa62086be3dc82a3 upstream.

Bugzilla bug 31422 reports occasional "page allocation failure. order:4"
at Squashfs mount time.  Fix this by making zlib workspace allocation
use vmalloc rather than kmalloc.

Reported-by: Mehmet Giritli <mehmet@giritli.eu>
Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>