Simplify the handling of different ERTM header size. We were the same
check in some places of the code, and more is expected to come, so just
replace them with a function.
Signed-off-by: NGustavo Padovan <gustavo.padovan@collabora.co.uk>
Acked-by: NAndrei Emeltchenko <andrei.emeltchenko@intel.com>
Signed-off-by: NJohan Hedberg <johan.hedberg@intel.com>