drm: bridge: it66121: Fix invalid connector dereference

drm: bridge: it66121: Fix invalid connector dereference

[ Upstream commit d0375f6858c4ff7244b62b02eb5e93428e1916cd ]

Fix the NULL pointer dereference when no monitor is connected, and the
sound card is opened from userspace.

Instead return an empty buffer (of zeroes) as the EDID information to
the sound framework if there is no connector attached.

Fixes: e0fd83dbe924 ("drm: bridge: it66121: Add audio support")
Reported-by: Nishanth Menon <nm@ti.com>
Closes: https://lore.kernel.org/all/20230825105849.crhon42qndxqif4i@gondola/
Reviewed-by: Helen Koike <helen.koike@collabora.com>
Signed-off-by: Jai Luthra <j-luthra@ti.com>
Tested-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Aradhya Bhatia <a-bhatia1@ti.com>
Signed-off-by: Robert Foss <rfoss@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230901-it66121_edid-v2-1-aa59605336b9@ti.com
Signed-off-by: Sasha Levin <sashal@kernel.org>