s390: use sync regs for register transfer

s390: use sync regs for register transfer

Newer kernels provide the guest registers in kvm_run. Lets use
those if available (i.e. the capability is set). This avoids
ioctls on cpu_synchronize_state making intercepts faster.

In addition, we have now the prefix register, the access registers
the control registers up to date. This helps in certain cases,
e.g. for resolving kernel module addresses with gdb on a guest.

On return, we update the registers according to the level statement,
i.e. we put all registers for KVM_PUT_FULL_STATE and _RESET_STATE.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
Signed-off-by: Alexander Graf <agraf@suse.de>