net: ipa: fix kerneldoc comments

This commit affects comments (and in one case, whitespace) only.

Throughout the IPA code, return statements are documented using
"@Return:", whereas they should use "Return:" instead.  Fix these
mistakes.

In function definitions, some parameters are missing their comment
to describe them.  And in structure definitions, some fields are
missing their comment to describe them.  Add these missing
descriptions.

Some arguments changed name and type along the way, but their
descriptions were not updated (an endpoint pointer is now used in
many places that previously used an endpoint ID).  Fix these
incorrect parameter descriptions.

In the description for the ipa_clock structure, one field had a
semicolon instead of a colon in its description.  Fix this.

Add a missing function description for ipa_gsi_endpoint_data_empty().

All of these issues were identified when building with "W=1".

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>