drm/i915/huc: fix intel_huc.c doc bulleted list format error

Fix the following make htmldocs errors/warnings:

./drivers/gpu/drm/i915/gt/uc/intel_huc.c:29: ERROR: Unexpected indentation.
./drivers/gpu/drm/i915/gt/uc/intel_huc.c:30: WARNING: Block quote ends without a blank line; unexpected unindent.
./drivers/gpu/drm/i915/gt/uc/intel_huc.c:35: WARNING: Bullet list ends without a blank line; unexpected unindent.

This output is a bit misleading. The real issue here is we need a blank
line before and after the bulleted list.

Link: https://www.kernel.org/doc/html/latest/gpu/i915.html#huc
Link: https://lore.kernel.org/dri-devel/20230530152958.1384061-1-daniele.ceraolospurio@intel.com/

Signed-off-by: David Reaver <me@davidreaver.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230727025400.372965-1-me@davidreaver.com