accel/kvm: Always define AccelOpsClass::supports_guest_debug

Whether TARGET_KVM_HAVE_GUEST_DEBUG is defined or not,
kvm_supports_guest_debug() still exists and can be called.

Signed-off-by: Philippe Mathieu-Daudé <philmd@oss.qualcomm.com>
Reviewed-by: Daniel Henrique Barboza <daniel.barboza@oss.qualcomm.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20260705215729.62196-10-philmd@oss.qualcomm.com>