Request to ME to prepare the encrypted session key.

On Success, ME provides Encrypted session key. Function populates
the HDCP2.2 authentication msg SKE_Send_Eks.

v2: Rebased.
v3:
  cldev is passed as first parameter [Tomas]
  Redundant comments and cast are removed [Tomas]
v4:
  %zd for ssize_t [Alexander]
  %s/return -1/return -EIO [Alexander]
  Style fixed [Uma]
v5: Rebased.
v6:
  Collected the Rb-ed by.
  Rebasing.
v7:
  Adjust to the new mei interface.
  Fix for Kdoc.
v8:
  K-Doc addition. [Tomas]
v9:
  renamed func as mei_hdcp_* [Tomas]
  Inline function is defined for DDI index [Tomas]
v10:
  K-Doc fix. [Tomas]
v11:
  Rebased.
Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Acked-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/1550772730-23280-11-git-send-email-ramalingam.c@intel.com