Effectively revert "gpu: ion: replace __GFP_ZERO with manual zero'ing"

	commit d21375bd0e3b5c9fb1bfd341abb294349ca2507f
	Author: Mitchel Humpherys <mitchelh@codeaurora.org>
	Date:   Thu Jan 31 10:30:40 2013 -0800

	    gpu: ion: replace __GFP_ZERO with manual zero'ing

	    As a performance optimization, omit the __GFP_ZERO flag when
	    allocating individual pages and, instead, zero out all of the pages in
	    one fell swoop.

	    CRs-Fixed: 449035
	    Change-Id: Ieb9a895d8792727a8a40b1e27cb1bbeae098f581
	    Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>

b/18402205 External reports: Video playback failing on Flo after upgrade to
	   Lollipop

Change-Id: Ibd07d3ac0edd11278306d4dbe72050408cc8e09b
Signed-off-by: Iliyan Malchev <malchev@google.com>