kvmtool: arm: Work around missing PMU on AArch32

We don't have PMU support on 32bit ARM just yet, so let's work
around this the ugly way for now.

Cc: Will Deacon <will.deacon@arm.com>
Reported-by: Riku Voipio <riku.voipio@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>