Properly handle case where /etc/platform is empty

If hnvram is broken, /etc/platform is empty. Fix two predicates that do
not return the intended result in this situation. For example, the
predicate

contains "GFRG200 GFRG210 GFRG250" "$(cat /etc/platform)"

returns true if /etc/platform is empty.

Without this change, the kernel is flooding the console with this error
message:

mwifiex_pcie: info: mwifiex_pcie_interrupt: card=  (null) adapter=
(null)

I suspect that there is a race condition where it runs

echo 1 > /sys/bus/pci/devices/0000:01:00.0/remove

while the mwifiex interrupt handler is still registered.

This problem has been observed on a Prowl with a broken HNVRAM
partition.

Change-Id: I8ef20543026a1dab612820ec797850ad6d2523c4
1 file changed