drm: split build lists one per line and sort

While it takes more vertical space, sorted build lists with one object
per line are arguably easier to manage, especially when there are
conflicting changes.

Split anything with more than one object file.

v2: also split drm_cache.o and put it after drm_bridge.o (Andi)

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Acked-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20221011140830.3257655-1-jani.nikula@intel.com