Register hfi_rip_zero_padding.

Also, sort the hfi[] array to be in the same order as the declarations
of the fields, to make it easier to check that all fields are being
registered.

Change-Id: Ida530590ebd00bbf206e0f6041b8da880bce2c6f
Reviewed-on: https://code.wireshark.org/review/4089
Reviewed-by: Guy Harris <guy@alum.mit.edu>