[Hexagon] Add missing assignment to Itinerary in Call_nr

The class definition for Call_nr has the itinerary as a
parameter, but the value is never assigned to the Itinerary
field for the instruction. This means the compiler is unable
to schedule and packetize the instruction correctly because
these instrution will not have any resource descritions.
I don't have a specific test case, but the ps_call_nr.ll
test failed with a proposed patch.

llvm-svn: 345442