Default huge page size to the regular page size

With this simple tweak, vpp is OK for "make test" or non-dpdk driver
operation over a kernel which doesn't support hugepages at all.

Tested on a Raspberry-pi 3B+ running the Ubuntu 18.04 64-bit server
beta image. It's amazing that such a minimal system will not only
self-compile vpp, but also run the unit tests. It's slow, but what do
you expect for that amount of money?

Change-Id: I7f080f871c828cc4b44be13809495278fadbd717
Signed-off-by: Dave Barach <dave@barachs.net>