linux-imx

ppp: mppe: sanity error path rework

We are going to need sanity error path a little further, rework to be
able to use the sanity error path anywhere in decompressor.

Signed-off-by: Sylvain Rochet <sylvain.rochet@finsecur.com>
Signed-off-by: David S. Miller <davem@davemloft.net>