drm/i915/dp: stylistic cleanup around hdcp2_msg_data

Split struct declaration and array definition. Fix indents and
whitespace. No functional changes.

Cc: Ramalingam C <ramalingam.c@intel.com>
Reviewed-by: Ramalingam C <ramalingam.c@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190820134019.13229-1-jani.nikula@intel.com