Add missing format specifier.
Add missing format specifier.

Pointed out by LLVM.

db_disasm.c:1018:13: error: format string is not a string literal (potentially insecure)

ok miod@

orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars