When "bus_prot_reg_update" is true, the driver should use
INFRA_TOPAXI_PROTECTEN for both setting and clearing the bus
protection. However, the driver does not use this mask for
clearing bus protection which causes failure when booting
the imgtec gpu.

Corrected and tested with mt8173 chromebook.
Signed-off-by: Bilal Wasim <Bilal.Wasim@imgtec.com>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Reviewed-by: Hsin-Yi Wang <hsinyi@chromium.org>
Link: https://lore.kernel.org/r/20210701114012.RESEND.1.I27436c29c3bede46dcf86df696f48683662d1ec1@changeidSigned-off-by: Matthias Brugger <matthias.bgg@gmail.com>