Staging: android: binder: Allow using highmem for binder buffers

The default kernel mapping for the pages allocated for the binder
buffers is never used. Set the __GFP_HIGHMEM flag when allocating
these pages so we don't needlessly use low memory pages that may
be required elsewhere.

Signed-off-by: Arve Hjønnevåg <arve@android.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>