KVM: x86/pmu: Manipulate FIXED_CTR_CTRL MSR with macros

KVM: x86/pmu: Manipulate FIXED_CTR_CTRL MSR with macros

Magic numbers are used to manipulate the bit fields of
FIXED_CTR_CTRL MSR. This makes reading code become difficult, so use
pre-defined macros to replace these magic numbers.

Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Link: https://lore.kernel.org/r/20240430005239.13527-3-dapeng1.mi@linux.intel.com
[sean: drop unnecessary curly braces]
Signed-off-by: Sean Christopherson <seanjc@google.com>