kbuild: change filechk to surround the given command with { }

filechk_* rules often consist of multiple 'echo' lines. They must be
surrounded with { } or ( ) to work correctly. Otherwise, only the
string from the last 'echo' would be written into the target.

Let's take care of that in the 'filechk' in scripts/Kbuild.include
to clean up filechk_* rules.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

scripts/Makefile.lib

@@ -417,7 +417,6 @@ endef
 # Use filechk to avoid rebuilds when a header changes, but the resulting file
 # does not
 define filechk_offsets
-	( \
 	 echo "#ifndef $2"; \
 	 echo "#define $2"; \
 	 echo "/*"; \
@@ -428,5 +427,5 @@ define filechk_offsets
 	 echo ""; \
 	 sed -ne $(sed-offsets) < $<; \
 	 echo ""; \
-	 echo "#endif" )
+	 echo "#endif"
 endef