drm/i915/hdcp: Handle HDCP Line Rekeying for HDCP 1.4

drm/i915/hdcp: Handle HDCP Line Rekeying for HDCP 1.4

TRANS_DDI_FUNC_CTL asks us to disable hdcp line rekeying when not in
hdcp 2.2 and we are not using an hdmi transcoder and it need to be
enabled when we are using an HDMI transcoder to enable HDCP 1.4.
We use intel_de_rmw cycles to update TRANS_DDI_FUNC_CTL register so
we cannot depend on the value being 0 by default everytime which calls
for seprate handling of HDCP 1.4 case.

--v2
-Use the exising function and modify it based on a bool rather than
have a different function [Matt]

--v3
-No need for kzalloc [Jani]

--v4
-i915_reg_t should not be pointer [Jani]
-use rekey_bit to ensure when writing to reg everything is initialized

Bspec: 69964, 50493, 50054
Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241107022807.869744-1-suraj.kandpal@intel.com