x86/mce: Mark mce_end() noinstr

It is called by the #MC handler which is noinstr.

Fixes

  vmlinux.o: warning: objtool: do_machine_check()+0xbd6: call to memset() leaves .noinstr.text section

Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20211208111343.8130-9-bp@alien8.de