net/ice/base: allow GTP-U filter using only inner protocols

net/ice/base: allow GTP-U filter using only inner protocols

Adds a support for switch filter: GTP-U using just inner fields.
If user doesn't specify outer protocol and its fields but wants to
add switch filter for GTP-U using inner protocols and related fields
such as inner L3 and/or inner L4, this patch enables such filtering.

Signed-off-by: Kiran Patil <kiran.patil@intel.com>
Signed-off-by: Qi Zhang <qi.z.zhang@intel.com>
Acked-by: Qiming Yang <qiming.yang@intel.com>