kdump-lib.sh: detect secure boot on s390

On s390, if Secure-IPL is enabled, then "kexec -s -l" is required.
Otherwise kdump kernel can not be loaded.

Signed-off-by: Pingfan Liu <piliu@redhat.com>
Acked-by: Kairui Song <kasong@redhat.com>

kdump-lib.sh

@@ -612,6 +612,7 @@ is_secure_boot_enforced()
 		return 0
     fi
 
+    # Detect secure boot on x86 and arm64
     secure_boot_file=$(find /sys/firmware/efi/efivars -name SecureBoot-* 2>/dev/null)
     setup_mode_file=$(find /sys/firmware/efi/efivars -name SetupMode-* 2>/dev/null)
 
@@ -624,6 +625,11 @@ is_secure_boot_enforced()
         fi
     fi
 
+    # Detect secure boot on s390x
+    if [[ -e "/sys/firmware/ipl/secure" && "$(cat /sys/firmware/ipl/secure)" == "1" ]]; then
+        return 0
+    fi
+
     return 1
 }