We can continue to read the error log (up to MAX size) even if
we get the elog size more than MAX size. Hence change BUG_ON to
WARN_ON.

Also updated error message.
Reported-by: NGopesh Kumar Chaudhary <gopchaud@in.ibm.com>
Signed-off-by: NVasant Hegde <hegdevasant@linux.vnet.ibm.com>
Signed-off-by: NAnanth N Mavinakayanahalli <ananth@in.ibm.com>
Acked-by: NDeepthi Dharwar <deepthi@linux.vnet.ibm.com>
Acked-by: NStewart Smith <stewart@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>