python/qemu: accel: Strengthen kvm_available() checks

python/qemu: accel: Strengthen kvm_available() checks

Currently kvm_available() checks for the presence of kvm module
and, if target and host arches don't mismatch. This patch adds
an 3rd checking: if QEMU binary was compiled with kvm
support.

Signed-off-by: Wainer dos Santos Moschetta <[email protected]>
Reviewed-by: Alex Bennée <[email protected]>
Reviewed-by: Cleber Rosa <[email protected]>
Reviewed-by: Philippe Mathieu-Daudé <[email protected]>
Tested-by: Cleber Rosa <[email protected]>
Message-Id: <20191216191438[email protected]>
Signed-off-by: Cleber Rosa <[email protected]>