drm/i915: Typo fix - 'pipe bpc' to 'pipe bpp'

Noticed this while I was looking at some debug output,
 [drm:intel_hdmi_compute_config [i915]] picking bpc to 12 for HDMI output
 [drm:intel_hdmi_compute_config [i915]] forcing pipe bpc to 36 for HDMI

I believe the second line should be pipe *bpp*

Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1491329765-14340-1-git-send-email-dhinakaran.pandiyan@intel.com