Replace platform check with actual sysfs check
Replace platform check with actual sysfs check

Instead of checking for "platform" through odd means, just check
that the sysfs file we're looking for exists

Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>
Acked-by: Benjamin Herrenschmidt <a7089bb6e7e92505d88aaff006cbdd60cc9120b6@kernel.crashing.org>

leitao/ppc64-diag,leitao/ppc64-diag,leitao/ppc64-diag,leitao/ppc64-diag