riscv: kvm: define vcpu_sbi_ext_pmu in header

Sparse is giving a warning about vcpu_sbi_ext_pmu not being
defined, so add a definition to the relevant header to fix
the following:

arch/riscv/kvm/vcpu_sbi_pmu.c:81:37: warning: symbol 'vcpu_sbi_ext_pmu' was not declared. Should it be static?

Fixes: cbddc4c4 ("RISC-V: KVM: Add SBI PMU extension support")
Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Reviewed-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Anup Patel <anup@brainfault.org>

arch/riscv/include/asm/kvm_vcpu_sbi.h

@@ -72,4 +72,7 @@ extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_hsm;
 extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_experimental;
 extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_vendor;
 
+#ifdef CONFIG_RISCV_PMU_SBI
+extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_pmu;
+#endif
 #endif /* __RISCV_KVM_VCPU_SBI_H__ */

arch/riscv/kvm/vcpu_sbi.c

@@ -20,9 +20,7 @@ static const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_v01 = {
 };
 #endif
 
-#ifdef CONFIG_RISCV_PMU_SBI
-extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_pmu;
-#else
+#ifndef CONFIG_RISCV_PMU_SBI
 static const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_pmu = {
 	.extid_start = -1UL,
 	.extid_end = -1UL,