net/ice/base: replace single-element array hack

net/ice/base: replace single-element array hack

Convert the pre-C90-extension "C struct hack" method (using a single-
element array at the end of a structure for implementing variable-length
types) to the preferred use of C99 flexible array member.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Signed-off-by: Qi Zhang <qi.z.zhang@intel.com>
Acked-by: Qiming Yang <qiming.yang@intel.com>