drm/bridge: adv7511: Fix Intermittent EDID failures

In the process of adding support for shared IRQ pins, a scenario
was accidentally created where adv7511_irq_process returned
prematurely causing the EDID to fail randomly.

Since the interrupt handler is broken up into two main helper functions,
update both of them to treat the helper functions as IRQ handlers. These
IRQ routines process their respective tasks as before, but if they
determine that actual work was done, mark the respective IRQ status
accordingly, and delay the check until everything has been processed.

This should guarantee the helper functions don't return prematurely
while still returning proper values of either IRQ_HANDLED or IRQ_NONE.

Reported-by: Liu Ying <victor.liu@nxp.com>
Fixes: f3d96833 ("drm/bridge: adv7511: Allow IRQ to share GPIO pins")
Signed-off-by: Adam Ford <aford173@gmail.com>
Tested-by: Liu Ying <victor.liu@nxp.com> # i.MX8MP EVK ADV7535 EDID retrieval w/o IRQ
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240630221931.1650565-1-aford173@gmail.com


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

V3:  Remove unnecessary declaration of ret by evaluating the return
     code of regmap_read directly.

V2:  Fix uninitialized cec_status
     Cut back a little on error handling to return either IRQ_NONE or
     IRQ_HANDLED.