drm/i915/xe2lpd: Update C20 algorithm to include tx_misc

drm/i915/xe2lpd: Update C20 algorithm to include tx_misc

There has been an update to the BSpec in which we need to set
tx_misc=0x5 field for C20 TX Context programming for HDMI TMDS for
Xe2_LPD and newer. That field is mapped to the bits 7:0 of
SRAM_GENERIC_<A/B>_TX_CNTX_CFG_1, which in turn translates to tx[1] of
our state struct. Update the algorithm to reflect this change.

v2:
  - Fix Bspec reference (Sai Teja)
  - Use struct intel_display instead of drm_i915_private. (Jani)
  - Use the correct bit width for C20_PHY_TX_MISC_MASK. (Jani)

Bspec: 74491
Cc: Dnyaneshwar Bhadane <dnyaneshwar.bhadane@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Sai Teja Pottumuttu <sai.teja.pottumuttu@intel.com> #v1
Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241023153352.144146-3-gustavo.sousa@intel.com