net: ipa: make ipa_table_hash_support() a real function

With the exception of ipa_table_hash_support(), nothing defined in
"ipa_table.h" requires the full definition of the IPA structure.

Change that function to be a "real" function rather than an inline,
to avoid requring the IPA structure to be defined.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>