cxl: Fix -Werror=return-type in cxl_decoder_detach()

Fix following compiling errors:
In file included from ../drivers/cxl/core/pmu.c:10:
../drivers/cxl/core/core.h: In function ‘cxl_decoder_detach’:
../drivers/cxl/core/core.h:65:1: error: no return statement in function returning non-void [-Werror=return-type]
 }
 ^
cc1: some warnings being treated as errors
  CC [M]  drivers/nvdimm/claim.o
make[6]: *** [../scripts/Makefile.build:287: drivers/cxl/core/pmu.o] Error 1
make[6]: *** Waiting for unfinished jobs....
  CC [M]  drivers/infiniband/core/verbs.o

Fixes: b3a8822 ("cxl/region: Consolidate cxl_decoder_kill_region() and cxl_region_detach()")
Signed-off-by: Li Zhijian <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Dave Jiang <[email protected]>

Author: zhijianli88

drivers/cxl/core/core.h

@@ -62,6 +62,7 @@ static inline int cxl_decoder_detach(struct cxl_region *cxlr,
 				     struct cxl_endpoint_decoder *cxled,
 				     int pos, enum cxl_detach_mode mode)
 {
+	return 0;
 }
 static inline int cxl_region_init(void)
 {