target/riscv/kvm.c: add kvmconfig_get_cfg_addr() helper

There are 2 places in which we need to get a pointer to a certain
property of the cpu->cfg struct based on property offset. Next patch
will add a couple more.

Create a helper to avoid repeating this code over and over.

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20230706101738.460804-20-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/kvm.c

@@ -215,20 +215,23 @@ static KVMCPUConfig kvm_multi_ext_cfgs[] = {
     KVM_EXT_CFG("svpbmt", ext_svpbmt, KVM_RISCV_ISA_EXT_SVPBMT),
 };
 
+static void *kvmconfig_get_cfg_addr(RISCVCPU *cpu, KVMCPUConfig *kvmcfg)
+{
+    return (void *)&cpu->cfg + kvmcfg->offset;
+}
+
 static void kvm_cpu_cfg_set(RISCVCPU *cpu, KVMCPUConfig *multi_ext,
                             uint32_t val)
 {
-    int cpu_cfg_offset = multi_ext->offset;
-    bool *ext_enabled = (void *)&cpu->cfg + cpu_cfg_offset;
+    bool *ext_enabled = kvmconfig_get_cfg_addr(cpu, multi_ext);
 
     *ext_enabled = val;
 }
 
 static uint32_t kvm_cpu_cfg_get(RISCVCPU *cpu,
                                 KVMCPUConfig *multi_ext)
 {
-    int cpu_cfg_offset = multi_ext->offset;
-    bool *ext_enabled = (void *)&cpu->cfg + cpu_cfg_offset;
+    bool *ext_enabled = kvmconfig_get_cfg_addr(cpu, multi_ext);
 
     return *ext_enabled;
 }