target/arm: Remove KVM support for 32-bit Arm hosts

We deprecated the support for KVM on 32-bit Arm hosts in time
for release 5.0, which means that our deprecation policy allows
us to drop it in release 5.2. Remove the code.

To repeat the rationale from the deprecation note: the Linux
kernel dropped support for 32-bit Arm KVM hosts in 5.7.

Running 32-bit guests on a 64-bit Arm host remains supported.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20200904154156.31943-2-peter.maydell@linaro.org