gdb/testsuite: recognize one more unsupported instruction in gdb.reverse/step-precsav...

gdb/testsuite: recognize one more unsupported instruction in gdb.reverse/step-precsave.exp

When running this test on a processor that supports AVX512 (AMD EPYC
9634) on Debian 12 bookwork (system compiler is gcc 12.2.0), I see:

    continue^M
    Continuing.^M
    Process record does not support instruction bound.^M
    Process record does not support instruction 0x62 at address 0x7ffff7f49b40.^M
    Process record: failed to record execution log.^M
    ^M
    Program stopped.^M
    0x00007ffff7f49b40 in ?? () from /lib/x86_64-linux-gnu/libc.so.6^M
    (gdb) FAIL: gdb.reverse/step-precsave.exp: run to end of main

The instruction at this address is:

   0x00007ffff7f49b40:	62 e2 7d 48 7a c6   vpbroadcastb %esi,%zmm16

This seems like an AVX512 instruction (given the use of zmm16).  Match
this byte value in order to produce a KFAIL.

Change-Id: I1d20357fa538ba60b9c537160acf511a37d751ee
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30807
Approved-By: Tom Tromey <tom@tromey.com>