drm/i915: s/fbc_fc/fbc_false_color/

We're not that short on characters that we can't spell out
"false_color". Saves me from figuring out what "fc" means
the next time look at the code.

Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170606124412.5335-1-ville.syrjala@linux.intel.com


Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>