clocksource/drivers/tegra: Fix IO endianness

clocksource/drivers/tegra: Fix IO endianness

Support big-endian kernel by using endian-aware register access
functions.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Acked-by: Thierry Reding <treding@nvidia.com>
Cc: ben.dooks@codethink.co.uk
Cc: hdegoede@redhat.com
Cc: laurent.pinchart+renesas@ideasonboard.com
Cc: linux-arm-kernel@lists.infradead.org
Cc: maxime.ripard@free-electrons.com
Cc: viresh.kumar@linaro.org
Link: http://lkml.kernel.org/r/1427746633-9137-9-git-send-email-daniel.lezcano@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>