drm/xe: Add test for GT workarounds and tunings

In order to avoid mistakes when populating the workarounds, it's good to
be able to test if the entries added are all compatible for a certain
platform. The platform itself is not needed as long as we create fake
devices with enough configuration for the RTP helpers to process the
tables.  Common mistakes that can be avoided:

	- Entries clashing the bitfields being updated
	- Register type being mixed (MCR vs regular / masked vs regular)
	- Unexpected errors while adding the reg_sr entry

To test, inject a duplicate entry in gt_was, but with platform == tigerlake
rather than the currenct graphics version check:

       { XE_RTP_NAME("14011059788"),
	 XE_RTP_RULES(PLATFORM(TIGERLAKE)),
	 XE_RTP_ACTIONS(SET(GEN10_DFR_RATIO_EN_AND_CHICKEN, DFR_DISABLE))
       },

This produces the following result:

	$  ./tools/testing/kunit/kunit.py run \
		--kunitconfig drivers/gpu/drm/xe/.kunitconfig  xe_wa

	[14:18:02] Starting KUnit Kernel (1/1)...
	[14:18:02] ============================================================
	[14:18:02] ==================== xe_wa (1 subtest) =====================
	[14:18:02] ======================== xe_wa_gt  =========================
	[14:18:02] [drm:xe_reg_sr_add] *ERROR* Discarding save-restore reg 9550 (clear: 00000200, set: 00000200, masked: no): ret=-22
	[14:18:02]     # xe_wa_gt: ASSERTION FAILED at drivers/gpu/drm/xe/tests/xe_wa_test.c:116
	[14:18:02]     Expected gt->reg_sr.errors == 0, but
	[14:18:02]         gt->reg_sr.errors == 1 (0x1)
	[14:18:02] [FAILED] TIGERLAKE (B0)
	[14:18:02] [PASSED] DG1 (A0)
	[14:18:02] [PASSED] DG1 (B0)
	...

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Michał Winiarski <michal.winiarski@intel.com>
Link: https://lore.kernel.org/r/20230401085151.1786204-8-lucas.demarchi@intel.com