[contrib][linux] Add wrapper API

Add the kernel wrapper API. This keeps the same API and semantics as the
existing kernel API with name changes to be more kernel style and avoid
symbol collisions with zstd.

contrib/linux-kernel/Makefile

@@ -22,8 +22,6 @@ libzstd:
 		--xxh64-prefix 'xxh64' \
 		--rewrite-include '<limits\.h>=<linux/limits.h>' \
 		--rewrite-include '<stddef\.h>=<linux/types.h>' \
-		--rewrite-include '"\.\./zstd.h"=<linux/zstd.h>' \
-		--rewrite-include '"(\.\./common/)?zstd_errors.h"=<linux/zstd_errors.h>' \
 		-DZSTD_NO_INTRINSICS \
 		-DZSTD_NO_UNUSED_FUNCTIONS \
 		-DZSTD_LEGACY_SUPPORT=0 \
@@ -48,8 +46,7 @@ libzstd:
 		-U_WIN32 \
 		-RZSTDLIB_VISIBILITY= \
 		-RZSTDERRORLIB_VISIBILITY=
-	mv linux/lib/zstd/zstd.h linux/include/linux
-	mv linux/lib/zstd/common/zstd_errors.h linux/include/linux
+	cp linux_zstd.h linux/include/linux/zstd.h
 	cp zstd_compress_module.c linux/lib/zstd
 	cp zstd_decompress_module.c linux/lib/zstd
 	cp decompress_sources.h linux/lib/zstd
@@ -62,9 +59,8 @@ import: libzstd
 	rm -f $(LINUX)/include/linux/zstd.h
 	rm -f $(LINUX)/include/linux/zstd_errors.h
 	rm -rf $(LINUX)/lib/zstd
-	mv linux/include/linux/zstd.h $(LINUX)/include/linux
-	mv linux/include/linux/zstd_errors.h $(LINUX)/include/linux
-	mv linux/lib/zstd $(LINUX)/lib
+	cp linux/include/linux/zstd.h $(LINUX)/include/linux
+	cp -r linux/lib/zstd $(LINUX)/lib
 
 .PHONY: test
 test: libzstd