drm/i915: Fix plane init failure paths

Deal with errors from drm_universal_plane_init() in primary and cursor
plane init paths (sprites were already covered). Also make the code
neater by using goto for error handling.

v2: Rebased due to drm_universal_plane_init() 'name' parameter
v3: Another rebase due to s/""/NULL/
v4: Rebased on drm-nightly (Matthew Auld)
v5: Fix email address (Matthew Auld)

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1458571402-32749-1-git-send-email-matthew.auld@intel.com