drm/i915/icl: Disable pipe CSC and gamma in cursor plane

'Pipe CSC enable' bit is more than just deprecated in ICL+, it was
disabled in commit 077ef1f0

 ("drm/i915/icl: Don't set pipe
CSC/Gamma in PLANE_COLOR_CTL") for primary and sprite planes as it was
causing those planes to be rendered as always black but it was not
disabled in cursor plane, also causing it to be rendered as black.

As mentioned in the commit referenced above, this is a workaround
too and the CSC and gamma per plane values needs to be setup before
enable CSC and gamma again.

BSpec: 4278 and 7635

Cc: James Ausmus <james.ausmus@intel.com>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180518201547.15793-1-jose.souza@intel.com