target/arm/kvm: Drop support for kernels without KVM_ARM_PREFERRED_TARGET

target/arm/kvm: Drop support for kernels without KVM_ARM_PREFERRED_TARGET

Our KVM code includes backwards compatibility support for ancient
kernels which don't support the KVM_ARM_PREFERRED_TARGET ioctl.  This
ioctl was introduced in kernel commit 42c4e0c77ac91 in September
2013 and is in v3.12, so it's reasonable to assume it's present.

(We already dropped support for kernels without KVM_CAP_DEVICE_CTRL,
a feature added to the kernel in April 2013, in our commit
84f298ea3e; so there are only about six months' worth of kernels,
from v3.9 to v3.11, that we don't already fail to run on and that
this commit is dropping handling for.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20250318114222.1018200-1-peter.maydell@linaro.org