ice: Make ptype internal to descriptor info processing

ice: Make ptype internal to descriptor info processing

Currently, rx_ptype variable is used only as an argument
to ice_process_skb_fields() and is computed
just before the function call.

Therefore, there is no reason to pass this value as an argument.
Instead, remove this argument and compute the value directly inside
ice_process_skb_fields() function.

Also, separate its calculation into a short function, so the code
can later be reused in .xmo_() callbacks.

Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Larysa Zaremba <larysa.zaremba@intel.com>
Link: https://lore.kernel.org/r/20231205210847.28460-4-larysa.zaremba@intel.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>