net: nbuf: Initialize nbuf memory area after allocation
net: nbuf: Initialize nbuf memory area after allocation

After commit 71c7c018192b995b9f03bf9c14b164d78909420b about buf pool, we
started to get spurious behaviors on various places of the code on
different boards (a101, frdm...) BUT on qemu. Basically, outgoing ip/udp
packets were full of garbage. Or sometimes it was the abilitty to parse
incoming packet that was happening.

The difference between qemu and actualy boards is - afaik, at least, let
me know if I am wrong - that qemu provide initialized memory (full of
0s). Following this asssumption, this patch just reset the nbuf right
after it got allocated. And all started to work again as thought.

It's in fact a good thing to reset nbuf memory. Even before the above
commit: after being used more than once, a buffer would have ended up
with old content, and this could have been generating a bug. So let's be
on the safe side and always intialize nbuf content.

Change-Id: I50647d9e9b82a4ed340a5ceb0d69409b0194dddd
Signed-off-by: Tomasz Bursztyka <ba81a3a719836727e6857ae83462b9f52ec41006@linux.intel.com>

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