drm/i915/dp: Fix passing the correct DPCD_REV for drm_dp_set_phy_test_pattern

Using link_status to get DPCD_REV fails when disabling/defaulting
phy pattern. Use intel_dp->dpcd to access DPCD_REV correctly.

Fixes: 8cdf7271

 ("drm/i915/dp: Program vswing, pre-emphasis, test-pattern")
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Lee Shawn C <shawn.c.lee@intel.com>
Signed-off-by: Khaled Almahallawy <khaled.almahallawy@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231213211542.3585105-3-khaled.almahallawy@intel.com