gold: Update ver_test_pr16504.sh

gold: Update ver_test_pr16504.sh

commit df3a023bd614133fe69afb02cd0e8f3e590a36a9
Author: Alan Modra <amodra@gmail.com>
Date:   Tue Jul 23 17:54:42 2019 +0930

    SHF_GNU_MBIND requires ELFOSABI_GNU

changed readelf to print IFUNC only for ELFOSABI_GNU.  Since

$ readelf -h ver_test_pr16504.so
...
 OS/ABI:                            UNIX - System V
...

we get

$ readelf -sW ver_test_pr16504.so
...
     3: 0000000000000378    13 <OS specific>: 10 GLOBAL DEFAULT    9 foo@@VER1
...

Update ver_test_pr16504.sh to also accept "<OS specific>: 10".

	* testsuite/ver_test_pr16504.sh: Updated.