Merge branch 'net-is_enabled'

Javier Martinez Canillas says:

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net: use IS_ENABLED() instead of checking for built-in or module

This trivial series replace the open coding to check for a Kconfig symbol
being built-in or module, with IS_ENABLED() macro that does exactly that.

Using the macro makes the code more readable by helping abstract away some
of the Kconfig built-in and module enable details.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>