bus: ti-sysc: Fix dispc quirk masking bool variables

Fix warning drivers/bus/ti-sysc.c:1806 sysc_quirk_dispc()
warn: masking a bool.

While at it let's add a comment for what were doing to make
the code a bit easier to follow.

Fixes: 7324a7a0 ("bus: ti-sysc: Implement display subsystem reset quirk")
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/linux-omap/a8ec8a68-9c2c-4076-bf47-09fccce7659f@kili.mountain/


Signed-off-by: Tony Lindgren <tony@atomide.com>