doc: document all EAL parameters in one place

doc: document all EAL parameters in one place

Currently, the most complete (but still incomplete) user guide for
EAL command-line parameters resides in user guide for testpmd.
This is wrong on multiple levels, and should not be the case.

To fix it, we have to create a document that lists all supported
EAL command-line arguments. However, because different platforms
support different subsets of available EAL parameters, instead of
creating a single file, we will create a common file in
doc/guides/common containing documentation for EAL parameters
that are supported on all of our supported platforms (Linux and
FreeBSD at the time of this writing).

We will then include this document in the Getting Started guides
for all supported platforms, so that any changes made to
documentation for commonly supported EAL parameters will be
reflected in Getting Started guides for all platforms.

This patch also removes EAL parameters documentation from the
testpmd user guide, and instead adds references to the newly
created documents in both testpmd user guides and in sample
applications guide.

Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
Acked-by: Ferruh Yigit <ferruh.yigit@intel.com>
Reviewed-by: Rami Rosen <roszenrami@gmail.com>