drm/i915: wrapping all hdcp var into intel_hdcp

Considering significant number of HDCP specific variables, it will
be clean to have separate struct for HDCP.

New structure called intel_hdcp is added within intel_connector.

v2:
  struct hdcp statically allocated. [Sean Paul]
  enable and disable function parameters are retained.[Sean Paul]
v3:
  No Changes.
v4:
  Commit msg is rephrased [Uma]
v5:
  Comment for mutex definition.
v6:
  hdcp_ prefix from all intel_hdcp members are removed [Sean Paul]
  inline function intel_hdcp_to_connector is defined [Sean Paul]
v7:
  %s/uint64_t/u64
v8:
  Rebased

Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/1540806351-7137-2-git-send-email-ramalingam.c@intel.com