drm/xe: Declare __xe_lrc_*_ggtt_addr with __maybe__unused

Kernel test robot reports building error:

	drivers/gpu/drm/xe/xe_lrc.c:544:1: error: unused function
	'__xe_lrc_regs_ggtt_addr' [-Werror,-Wunused-function]
	544 | DECL_MAP_ADDR_HELPERS(regs)
	    | ^~~~~~~~~~~~~~~~~~~~~~~~~~~
	drivers/gpu/drm/xe/xe_lrc.c:536:19: note: expanded from macro
	'DECL_MAP_ADDR_HELPERS'
	536 | static inline u32 __xe_lrc_##elem##_ggtt_addr(struct xe_lrc *lrc) \

Declare __xe_lrc_*_ggtt_addr with __maybe_unused to address it.
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202402010928.g3j2aSBL-lkp@intel.com/Signed-off-by: Dawei Li <dawei.li@shingroup.cn>
Link: https://patchwork.freedesktop.org/patch/msgid/20240204062324.3548268-1-dawei.li@shingroup.cnSigned-off-by: Lucas De Marchi <lucas.demarchi@intel.com>

drivers/gpu/drm/xe/xe_lrc.c

@@ -655,7 +655,7 @@ static inline struct iosys_map __xe_lrc_##elem##_map(struct xe_lrc *lrc) \
 	iosys_map_incr(&map, __xe_lrc_##elem##_offset(lrc)); \
 	return map; \
 } \
-static inline u32 __xe_lrc_##elem##_ggtt_addr(struct xe_lrc *lrc) \
+static inline u32 __maybe_unused __xe_lrc_##elem##_ggtt_addr(struct xe_lrc *lrc) \
 { \
 	return xe_bo_ggtt_addr(lrc->bo) + __xe_lrc_##elem##_offset(lrc); \
 } \