kbuild: Fix <linux/version.h> for empty SUBLEVEL or PATCHLEVEL again

Commit 78d3bb4 ("kbuild: Fix <linux/version.h> for empty SUBLEVEL
or PATCHLEVEL") fixed the build error for empty SUBLEVEL or PATCHLEVEL
by prepending a zero.

Commit 9b82f13 ("kbuild: clamp SUBLEVEL to 255") re-introduced
this issue.

This time, we cannot take the same approach because we have C code:

  #define LINUX_VERSION_PATCHLEVEL $(PATCHLEVEL)
  #define LINUX_VERSION_SUBLEVEL $(SUBLEVEL)

Replace empty SUBLEVEL/PATCHLEVEL with a zero.

Fixes: 9b82f13 ("kbuild: clamp SUBLEVEL to 255")
Reported-by: Christian Zigotzky <[email protected]>
Signed-off-by: Masahiro Yamada <[email protected]>
Reviewed-and-tested-by: Sasha Levin <[email protected]>

Makefile

@@ -1284,10 +1284,10 @@ endef
 define filechk_version.h
 	if [ $(SUBLEVEL) -gt 255 ]; then                                 \
 		echo \#define LINUX_VERSION_CODE $(shell                 \
-		expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + 255); \
+		expr $(VERSION) \* 65536 + $(PATCHLEVEL) \* 256 + 255); \
 	else                                                             \
 		echo \#define LINUX_VERSION_CODE $(shell                 \
-		expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + $(SUBLEVEL)); \
+		expr $(VERSION) \* 65536 + $(PATCHLEVEL) \* 256 + $(SUBLEVEL)); \
 	fi;                                                              \
 	echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) +  \
 	((c) > 255 ? 255 : (c)))';                                       \
@@ -1296,6 +1296,8 @@ define filechk_version.h
 	echo \#define LINUX_VERSION_SUBLEVEL $(SUBLEVEL)
 endef
 
+$(version_h): PATCHLEVEL := $(if $(PATCHLEVEL), $(PATCHLEVEL), 0)
+$(version_h): SUBLEVEL := $(if $(SUBLEVEL), $(SUBLEVEL), 0)
 $(version_h): FORCE
 	$(call filechk,version.h)