powerpc/pseries/vas: Pass hw_cpu_id to node associativity HCALL

Generally the hypervisor decides to allocate a window on different
VAS instances. But if user space wishes to allocate on the current VAS
instance where the process is executing, the kernel has to pass
associativity domain IDs to allocate VAS window HCALL.

To determine the associativity domain IDs for the current CPU,
smp_processor_id() is passed to node associativity HCALL which may
return H_P2 (-55) error during DLPAR CPU event. This is because Linux
CPU numbers (smp_processor_id()) are not the same as the hypervisor's
view of CPU numbers.

Fix the issue by passing hard_smp_processor_id() with
VPHN_FLAG_VCPU flag (PAPR 14.11.6.1 H_HOME_NODE_ASSOCIATIVITY).

Fixes: b22f2d88 ("powerpc/pseries/vas: Integrate API with open/close windows")
Reviewed-by: Nathan Lynch <nathanl@linux.ibm.com>
Signed-off-by: Haren Myneni <haren@linux.ibm.com>
[mpe: Update change log to mention Linux vs HV CPU numbers]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/55380253ea0c11341824cd4c0fc6bbcfc5752689.camel@linux.ibm.com