KVM: ia64: fix fp fault/trap handler

The floating-point registers f6-f11 is used by vmm and
saved in kvm-pt-regs, so should set the correct bit mask
and the pointer in fp_state, otherwise, fpswa may touch
vmm's fp registers instead of guests'.

In addition, for fp trap handling,  since the instruction
which leads to fp trap is completely executed, so can't
use retry machanism to re-execute it, because it may
pollute some registers.

Signed-off-by: Yang Zhang <yang.zhang@intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>