Commits fc8c5b8c (Makefile.user: Define
CONFIG_USER_ONLY for libuser/) and
dd83b06a (qom: Introduce CPU class)
specifically prepared the qom/cpu.c file to be compiled differently for
softmmu and *-user. This broke as part of build system refactorings
while CPU patches were in flight, adding conditional fields
kvm_fd (8737c51c) and
kvm_vcpu_dirty (20d695a9) for softmmu.

linux-user and bsd-user would therefore get a CPUState type with
instance_size ~8 bytes longer than expected.
Fix this by unconditionally having the fields in CPUState.

In practice, target-specific CPU types' instance_size would compensate
this, and upstream qom/cpu.c does not yet touch any affected field.
Signed-off-by: NAndreas Färber <afaerber@suse.de>
Reviewed-by: NPaolo Bonzini <pbonzini@redhat.com>