drm/bridge: ite66121: Register HPD interrupt handler only when 'client->irq > 0'

If a specific design doesn't wire IT66121's interrupt signal output pin up
to the display controller side, then we should not register the interrupt
handler. Such a decision is valid usage, as we can fall back to polling
mode. So, don't make the assumption that a specific board always supports
HPD. Carry out a sanity check on 'client->irq' before using it, fall back
to polling mode if client->irq < 0 is true. Such a design increases the
overall flexibility.

Signed-off-by: Sui Jingfeng <sui.jingfeng@linux.dev>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20240316160536.1051513-1-sui.jingfeng@linux.dev


Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240316160536.1051513-1-sui.jingfeng@linux.dev