target/s390x: Simplify S390_ADAPTER_SUPPRESSIBLE definition

target/s390x: Simplify S390_ADAPTER_SUPPRESSIBLE definition

Commit 1497c160661 ("s390x: add flags field for registering I/O
adapter") defined S390_ADAPTER_SUPPRESSIBLE twice, one when
KVM is available and another when it isn't. However both
definitions expand to the same value. Unify them, adding an
extra safety check in KVM-specific file.

This allows removing the target-specific 'CONFIG_KVM'
definition in "cpu.h".

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-ID: <20260107130807.69870-15-philmd@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>