KVM: selftests: Drop unnecessary use of kvm_get_supported_cpuid_index()

Use kvm_get_supported_cpuid_entry() instead of
kvm_get_supported_cpuid_index() when passing in '0' for the index, which
just so happens to be the case in all remaining users of
kvm_get_supported_cpuid_index() except kvm_get_supported_cpuid_entry().

Keep the helper as there may be users in the future, and it's not doing
any harm.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20220614200707.3315957-36-seanjc@google.com

tools/testing/selftests/kvm/x86_64/amx_test.c

@@ -318,7 +318,7 @@ int main(int argc, char *argv[])
 	TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_XTILEDATA));
 
 	/* Get xsave/restore max size */
-	xsave_restore_size = kvm_get_supported_cpuid_index(0xd, 0)->ecx;
+	xsave_restore_size = kvm_get_supported_cpuid_entry(0xd)->ecx;
 
 	run = vcpu->run;
 	vcpu_regs_get(vcpu, &regs1);

tools/testing/selftests/kvm/x86_64/pmu_event_filter_test.c

@@ -402,7 +402,7 @@ static bool use_intel_pmu(void)
 {
 	const struct kvm_cpuid_entry2 *entry;
 
-	entry = kvm_get_supported_cpuid_index(0xa, 0);
+	entry = kvm_get_supported_cpuid_entry(0xa);
 	return is_intel_cpu() && check_intel_pmu_leaf(entry);
 }
 
@@ -434,7 +434,7 @@ static bool use_amd_pmu(void)
 {
 	const struct kvm_cpuid_entry2 *entry;
 
-	entry = kvm_get_supported_cpuid_index(1, 0);
+	entry = kvm_get_supported_cpuid_entry(1);
 	return is_amd_cpu() &&
 		(is_zen1(entry->eax) ||
 		 is_zen2(entry->eax) ||

tools/testing/selftests/kvm/x86_64/vmx_pmu_caps_test.c

@@ -69,7 +69,7 @@ int main(int argc, char *argv[])
 	TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_PDCM));
 
 	TEST_REQUIRE(kvm_get_cpuid_max_basic() >= 0xa);
-	entry_a_0 = kvm_get_supported_cpuid_index(0xa, 0);
+	entry_a_0 = kvm_get_supported_cpuid_entry(0xa);
 
 	eax.full = entry_a_0->eax;
 	__TEST_REQUIRE(eax.split.version_id, "PMU is not supported by the vCPU");