enh: guard x86/arm specific checks in kernel/cpu for the proper arch

src/vulns/CVE-2018-3640.sh

@@ -11,7 +11,7 @@ check_CVE_2018_3640() {
     sys_interface_available=0
     msg=''
 
-    if is_arm64_kernel; then
+    if is_arm_kernel; then
         # ARM64: mitigation is via an EL2 indirect trampoline (spectre_v3a_enable_mitigation),
         # applied automatically at boot for affected CPUs (Cortex-A57, Cortex-A72).
         # No microcode update is involved.