objtool/x86: Add UDB support
Per commit 85a2d4a890dc ("x86,ibt: Use UDB instead of 0xEA"), make
sure objtool also recognises UDB as a #UD instruction.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>