Prevent ioda_eeh_hub_diag() from clobbering itself when called by supplying
a per-PHB buffer for P7IOC hub diagnostic data. Take care to inform OPAL of
the correct size for the buffer.
[Small style change to the use of sizeof -- BenH]
Signed-off-by: Brian W Hart <hartb@linux.vnet.ibm.com> Acked-by: Gavin Shan <shangw@linux.vnet.ibm.com> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>