drm/i915: WARN if !HAS_PC8 when enabling/disabling PC8
drm/i915: WARN if !HAS_PC8 when enabling/disabling PC8

We already have some checks and shouldn't be reaching these places on
!HAS_PC8 platforms, but add a WARN,  just in case.

Signed-off-by: Paulo Zanoni <cc0e04a2103c45cd195651d976f79813d0f66bdf@intel.com>
Reviewed-by: Rodrigo Vivi <f714145d6ee82178e54021e0c168f56d17b53c9c@gmail.com>
Signed-off-by: Daniel Vetter <c1b6782c4af8f0673da8923a0702a1832e5940f4@ffwll.ch>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs