cpu: Unconditionalize CPUState fields

cpu: Unconditionalize CPUState fields

Commits fc8c5b8c41ee5ba69d7a2be63b02a08c7b0b155b (Makefile.user: Define
CONFIG_USER_ONLY for libuser/) and
dd83b06ae61cfa2dc4381ab49f365bd0995fc930 (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 (8737c51c0444f832c4e97d7eb7540eae457e08e4) and
kvm_vcpu_dirty (20d695a9254c1b086a456d3b79a3c311236643ba) 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: Andreas Färber <afaerber@suse.de>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>