target/i386: Add support for MCDT_NO in CPUID enumeration

target/i386: Add support for MCDT_NO in CPUID enumeration

CPUID.(EAX=7,ECX=2):EDX[bit 5] enumerates MCDT_NO. Processors enumerate
this bit as 1 do not exhibit MXCSR Configuration Dependent Timing (MCDT)
behavior and do not need to be mitigated to avoid data-dependent behavior
for certain instructions.

Since MCDT_NO is in a new sub-leaf, add a new CPUID feature word
FEAT_7_2_EDX. Also update cpuid_level_func7 by FEAT_7_2_EDX.

Signed-off-by: Tao Su <tao1.su@linux.intel.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Message-ID: <20230706054949.66556-3-tao1.su@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>