target-i386: check/enforce: Fix CPUID leaf numbers on error messages

The -cpu check/enforce warnings are printing incorrect information about the
missing flags. There are no feature flags on CPUID leaves 0 and 0x80000000, but
there were references to 0 and 0x80000000 in the table at
kvm_check_features_against_host().

This changes the model_features_t struct to contain the register number as
well, so the error messages print the correct CPUID leaf+register information,
instead of wrong CPUID leaf numbers.

This also changes the format of the error messages, so they follow the
"CPUID.<leaf>.<register>.<name> [bit <offset>]" convention used in Intel
documentation. Example output:

    $ qemu-system-x86_64 -machine pc-1.0,accel=kvm -cpu Opteron_G4,+ia64,enforce
    warning: host doesn't support requested feature: CPUID.01H:EDX.ia64 [bit 30]
    warning: host doesn't support requested feature: CPUID.01H:ECX.xsave [bit 26]
    warning: host doesn't support requested feature: CPUID.01H:ECX.avx [bit 28]
    warning: host doesn't support requested feature: CPUID.80000001H:ECX.abm [bit 5]
    warning: host doesn't support requested feature: CPUID.80000001H:ECX.sse4a [bit 6]
    warning: host doesn't support requested feature: CPUID.80000001H:ECX.misalignsse [bit 7]
    warning: host doesn't support requested feature: CPUID.80000001H:ECX.3dnowprefetch [bit 8]
    warning: host doesn't support requested feature: CPUID.80000001H:ECX.xop [bit 11]
    warning: host doesn't support requested feature: CPUID.80000001H:ECX.fma4 [bit 16]
    Unable to find x86 CPU definition
    $

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Reviewed-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>
