kbuild: remove cc-option switch from -Wframe-larger-than=

This CONFIG option was added by commit 35bb5b1e0e84 ("Add option to
enable -Wframe-larger-than= on gcc 4.4"). At that time, the cc-option
check was needed.

According to Documentation/process/changes.rst, the current minimal
supported version of GCC is 4.6, so you can assume GCC supports it.
Clang supports it as well.

Remove the cc-option switch and redundant comments.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
diff --git a/Makefile b/Makefile
index 86035d8..22bc7cc 100644
--- a/Makefile
+++ b/Makefile
@@ -729,7 +729,7 @@
 endif
 
 ifneq ($(CONFIG_FRAME_WARN),0)
-KBUILD_CFLAGS += $(call cc-option,-Wframe-larger-than=${CONFIG_FRAME_WARN})
+KBUILD_CFLAGS += -Wframe-larger-than=$(CONFIG_FRAME_WARN)
 endif
 
 stackp-flags-$(CONFIG_CC_HAS_STACKPROTECTOR_NONE) := -fno-stack-protector