hw/i386/fw_cfg: Include missing 'cpu.h' header

fw_cfg_build_feature_control() uses CPUID_EXT_VMX which is
defined in "target/i386/cpu.h".

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20230904124325.79040-4-philmd@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

hw/i386/fw_cfg.c

@@ -24,6 +24,7 @@
 #include "kvm/kvm_i386.h"
 #include "qapi/error.h"
 #include CONFIG_DEVICES
+#include "target/i386/cpu.h"
 
 struct hpet_fw_config hpet_cfg = {.count = UINT8_MAX};