Documentation/i915: Fix references to renamed files

WARNING: kernel-doc './scripts/kernel-doc -rst -enable-lineno -function Hardware workarounds ./drivers/gpu/drm/i915/intel_workarounds.c' failed with return code 1
WARNING: kernel-doc './scripts/kernel-doc -rst -enable-lineno -function Logical Rings, Logical Ring Contexts and Execlists ./drivers/gpu/drm/i915/intel_lrc.c' failed with return code 1
WARNING: kernel-doc './scripts/kernel-doc -rst -enable-lineno -internal ./drivers/gpu/drm/i915/intel_lrc.c' failed with return code 2

Fixes: 112ed2d3

 ("drm/i915: Move GraphicsTechnology files under gt/")
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/bd7dd29b9fb2101c954c8cfb2c3b4efc7d277045.1559656538.git.mchehab+samsung@kernel.org