[AArch64] Remove redundant calculation of plt stub destination for veneer

[AArch64] Remove redundant calculation of plt stub destination for veneer

elfNN_aarch64_size_stubs, the caller of aarch64_type_stub has redirected
the final destination of long branch veneer to plt stub if the call
should go through it.

It's redundant to do the same check and redirect again from scratch
inside aarch64_type_stub.

bfd/
  * elfnn-aarch64. (aarch64_type_of_stub): Remove redundation calcuation
  for destination.  Remove useless function parameters.
  (elfNN_aarch64_size_stubs): Update parameters for aarch64_type_of_stub.