x86: Check the lower byte of EAX of CPUID leaf 2 [BZ #30643]

x86: Check the lower byte of EAX of CPUID leaf 2 [BZ #30643]

The old Intel software developer manual specified that the low byte of
EAX of CPUID leaf 2 returned 1 which indicated the number of rounds of
CPUDID leaf 2 was needed to retrieve the complete cache information. The
newer Intel manual has been changed to that it should always return 1
and be ignored.  If the lower byte isn't 1, CPUID leaf 2 can't be used.
In this case, we ignore CPUID leaf 2 and use CPUID leaf 4 instead.  If
CPUID leaf 4 doesn't contain the cache information, cache information
isn't available at all.  This addresses BZ #30643.