enetc: Fix endianness issues for enetc_qos

Currently the control buffer descriptor (cbd) fields have endianness
restrictions while the commands passed into the control buffers
don't (with one exception). This patch fixes offending code,
by adding endianness accessors for cbd fields and removing the
unnecessary ones in case of data buffer fields. Currently there's
no need to convert all commands to little endian format, the patch
only focuses on fixing current endianness issues reported by sparse.

Signed-off-by: Claudiu Manoil <claudiu.manoil@nxp.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>