upic_ktrls: make RSS compile again here

The results of ktls_get_cpu() are stored in u_int and NETISR_CPUID_NONE
requires u_int. Adjust uint16_t to uint_t in order to make RSS kernels
compile some more again.

HPTS still has to be fixed, which is a bit more complicated.

Reviewed by: jhb, gallatin, rrs
Differential Revision: https://reviews.freebsd.org/D23726