CHROMIUM: ARM: r1->r0 for get/set arguments

ARM reuses r0 as the first argument. This fixes the mistaken
assumption in the original patchset.  These will be merged
into one change when sent upstream.

Signed-off-by: Will Drewry <wad@chromium.org>
TEST=emerge tegra2_kaen; run seccomp testsuite
BUG=chromium-os:27878

Change-Id: Iaaa09995d35f78ee8cef7b600d526e71f3b2fcec
Reviewed-on: https://gerrit.chromium.org/gerrit/21342
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Will Drewry <wad@chromium.org>
Tested-by: Will Drewry <wad@chromium.org>
Signed-off-by: Sasha Levitskiy <sanek@google.com>