drm/i915/hdmi: use generic poll_timeout_us() instead of __wait_for()

drm/i915/hdmi: use generic poll_timeout_us() instead of __wait_for()

Prefer generic poll helpers over i915 custom helpers.

The functional change is losing the exponentially growing sleep of
__wait_for(), which used to be 1, 2, 4, and 8 ms in this particular
case.

Use an arbitrary constant 4 ms sleep instead. The timeout remains,
varying between 20 ms and 3000 ms.

Cc: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Jouni Högander <jouni.hogander@intel.com>
Link: https://lore.kernel.org/r/fc3a67f9de0049f415a276bba1c11a4df97e01d6.1756383233.git.jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>