zdtm/x86: Don't override %ebx in fpu00

%ebx, %ecx aren't specified as clobbers in chk_proc_fpu(),
while asm cpuid overwrites them.

In the turn, %ebx is used as a code position by gcc now:
    1661:       e8 9a 00 00 00          call   1700 <__x86.get_pc_thunk.bx>
    1666:       81 c3 46 68 00 00       add    $0x6846,%ebx

Which results in dereferencing some ugly garbage (result of cpuid).

Let's use zdtm/lib cpuid() function instead.

Signed-off-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: Andrei Vagin <avagin@gmail.com>