drm/xe: Add basic unit tests for rtp

Add some basic unit tests for rtp. This is intended to prove the
functionality of the rtp itself, like coalescing entries, rejecting
non-disjoint values, etc.

Contrary to the other tests in xe, this is a unit test to test the
sw-side only, so it can be executed on any machine - it doesn't interact
with the real hardware. Running it produces the following output:

	$ ./tools/testing/kunit/kunit.py run --raw_output-kunit  \
		--kunitconfig drivers/gpu/drm/xe/.kunitconfig xe_rtp
	...
	[01:26:27] Starting KUnit Kernel (1/1)...
	KTAP version 1
	1..1
	    KTAP version 1
	    # Subtest: xe_rtp
	    1..1
		KTAP version 1
		# Subtest: xe_rtp_process_tests
		ok 1 coalesce-same-reg
		ok 2 no-match-no-add
		ok 3 no-match-no-add-multiple-rules
		ok 4 two-regs-two-entries
		ok 5 clr-one-set-other
		ok 6 set-field
	[drm:xe_reg_sr_add] *ERROR* Discarding save-restore reg 0001 (clear: 00000001, set: 00000001, masked: no): ret=-22
		ok 7 conflict-duplicate
	[drm:xe_reg_sr_add] *ERROR* Discarding save-restore reg 0001 (clear: 00000003, set: 00000000, masked: no): ret=-22
		ok 8 conflict-not-disjoint
	[drm:xe_reg_sr_add] *ERROR* Discarding save-restore reg 0001 (clear: 00000002, set: 00000002, masked: no): ret=-22
	[drm:xe_reg_sr_add] *ERROR* Discarding save-restore reg 0001 (clear: 00000001, set: 00000001, masked: yes): ret=-22
		ok 9 conflict-reg-type
	    # xe_rtp_process_tests: pass:9 fail:0 skip:0 total:9
	    ok 1 xe_rtp_process_tests
	# Totals: pass:9 fail:0 skip:0 total:9
	ok 1 xe_rtp
	...

Note that the ERRORs in the kernel log are expected since it's testing
incompatible entries.

v2:
  - Use parameterized table for tests  (Michał Winiarski)
  - Move everything to the xe_rtp_test.ko and only add a few exports to the
    right namespace
  - Add more tests to cover FIELD_SET, CLR, partially true rules, etc

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Maarten Lankhorst<maarten.lankhorst@linux.intel.com> # v1
Reviewed-by: Michał Winiarski <michal.winiarski@intel.com>
Link: https://lore.kernel.org/r/20230401085151.1786204-7-lucas.demarchi@intel.com