skbuff: Move rxhash and vlan_tci to consolidate holes in sk_buff

This change helps to reduce the overall size of the sk_buff by moving
rxhash and vlan_tci so that the u16 values and u8 bitfields can be better
combined to create only one hole instead of multiple.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Stephen Ko <stephen.s.ko@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>