drm/i915/dp: Increase idle pattern wait timeout to 2ms

drm/i915/dp: Increase idle pattern wait timeout to 2ms

The driver currently waits 1ms for idle patterns,
but for Xe2LPD and possibly future display IPs,
it requires a 1640us (rounded up to 2ms) timeout
whilst waiting for idle patterns for MST streams.

To simplify the code, the timeout is uniformly
increased by 1ms across all platforms/display IPs.

v1: Introduced the 2ms wait timeout.
v2: Segregated the wait timeout for platforms before & after LNL.
v3: Fixed 2 cosmetic changes.
v4: Revert to v2 design with commit message enhancements.
v5: Minor cosmetic changes to the commit message.

BSpec: 68849
Signed-off-by: Shekhar Chauhan <shekhar.chauhan@intel.com>
Reviewed-by: Gustavo Sousa <gustavo.sousa@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240311041504.806058-1-shekhar.chauhan@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>