drm: adv7511: Fix nested sleep when reading EDID

The EDID read code waits for the read completion interrupt to occur
using wait_event_interruptible(). The condition passed to the macro
reads I2C registers. This results in sleeping with the task state set
to TASK_INTERRUPTIBLE, triggering a WARN_ON() introduced in commit
8eb23b9f

 ("sched: Debug nested sleeps").

Fix this by reworking the EDID read code. Instead of checking whether
the read is complete through I2C reads, handle the interrupt registers
in the interrupt handler and update a new edid_read flag accordingly. As
a side effect both the IRQ and polling code paths now process the
interrupt sources through the same code path, simplifying the code.

Cc: stable@vger.kernel.org
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>