tools/x86/kcpuid: Check last token too

Input lines like

  0x8000001E,     0, EAX,   31:0, Extended APIC ID

where the short name is missing lead to a segfault because the loop
takes the long name for the short name and tokens[5] becomes NULL which
explodes later in strcpy().

Check its value too before further processing.

Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Feng Tang <feng.tang@intel.com>
Link: https://lkml.kernel.org/r/20210315125901.30315-1-bp@alien8.de