arm64: Kconfig: change fix compile error if gcc don't support armv8.4-a

hulk inclusion
category: feature
CVE: NA

-----------------------

After 4d0831e8 ("kconfig: unify cc-option and as-option")
in mainline, we can use cc-option.

But in linux-4.19, this patch is not merged, so we will get the
follow error:
  CC      scripts/mod/empty.o
  CC      scripts/mod/devicetable-offsets.s
Assembler messages:
Error: unknown architecture `armv8.4-a'

Error: unrecognized option -march=armv8.4-a

Fix this by changing cc-option to as-option.
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Reviewed-by: NHanjun Guo <guohanjun@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

arch/arm64/Kconfig

@@ -1307,7 +1307,7 @@ endmenu
 menu "ARMv8.4 architectural features"
 
 config AS_HAS_ARMV8_4
-	def_bool $(cc-option,-Wa$(comma)-march=armv8.4-a)
+	def_bool $(as-option,-Wa$(comma)-march=armv8.4-a)
 
 config ARM64_TLB_RANGE
 	bool "Enable support for tlbi range feature"