util/superiotool: Use c11 dialect

Change-Id: Ic03d9ac883a92d52467d563f048446871b928712
Signed-off-by: Elyes Haouas <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/82678
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Felix Singer <service+coreboot-gerrit@felixsinger.de>
diff --git a/util/superiotool/Makefile b/util/superiotool/Makefile
index fe2a4cc..39839d9 100644
--- a/util/superiotool/Makefile
+++ b/util/superiotool/Makefile
@@ -12,7 +12,7 @@
 VERSION := -D'SUPERIOTOOL_VERSION="$(shell git describe 2>/dev/null)"'
 
 CFLAGS += -O2 -Wall -Wstrict-prototypes -Wundef -Wstrict-aliasing \
-         -Werror-implicit-function-declaration -std=c99 -pedantic $(VERSION) \
+         -Werror-implicit-function-declaration -std=c11 -pedantic $(VERSION) \
          -Wno-variadic-macros -I $(TOP)/src/commonlib/bsd/include
 LDFLAGS += -lz
 
@@ -25,7 +25,7 @@
 endif
 ifeq ($(OS_ARCH), FreeBSD)
 CFLAGS = -O2 -Wall -Werror -Wstrict-prototypes -Wundef -Wstrict-aliasing \
-         -Werror-implicit-function-declaration -std=c99 $(VERSION) \
+         -Werror-implicit-function-declaration -std=c11 $(VERSION) \
          -I/usr/local/include
 LDFLAGS += -L/usr/local/lib
 LIBS = -lz