commit 7132813c upstream.

Current implementation doesn't zero out the pages allocated.
Honor the __GFP_ZERO flag and zero out if set.
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
[ luis: backported to 3.16: based on Suzuki's 3.14 backport ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>