net: Enable logging in more modules if CONFIG_NET_LOG_GLOBAL defined

This is useful to enable error/warning logging across the net
codebase (less useful for debug level logging, but that's true
for CONFIG_NET_LOG_GLOBAL already).

Implementation-wise, instead of keeping adding to long list of
"select"'s in CONFIG_NET_LOG_GLOBAL and thus introduce component
inter-dependencies, add "default y if NET_LOG_GLOBAL" to
individual components' logging options.

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>