[AArch64][SME] Update DUP (predicate) instruction

Changes in architecture revision 00eac1:
  * Renamed to PSEL.
  * Copies whole source register.
  * Element type suffix removed from destination.
  * Element index no longer optional and '#' prefix has been removed.

The reference can be found here:
https://developer.arm.com/documentation/ddi0602/2021-09

Depends on D111212.

Reviewed By: kmclaughlin

Differential Revision: https://reviews.llvm.org/D111213