x86/ibt,entry: Sprinkle ENDBR dust

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2090231



commit 8f93402b
Author: Peter Zijlstra <peterz@infradead.org>
Date:   Tue, 8 Mar 2022 16:30:24 +0100

    x86/ibt,entry: Sprinkle ENDBR dust

    Kernel entry points should be having ENDBR on for IBT configs.

    The SYSCALL entry points are found through taking their respective
    address in order to program them in the MSRs, while the exception
    entry points are found through UNWIND_HINT_IRET_REGS.

    The rule is that any UNWIND_HINT_IRET_REGS at sym+0 should have an
    ENDBR, see the later objtool ibt validation patch.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
    Link: https://lore.kernel.org/r/20220308154317.933157479@infradead.org



Signed-off-by: Waiman Long <longman@redhat.com>