[AArch64][SME] Support ptrue(s) in streaming mode

The ptrue and ptrues instructions are legal in streaming mode, missed in
D106272.

The reference can be found here:
https://developer.arm.com/documentation/ddi0602/2021-06/SVE-Instructions

Reviewed By: paulwalker-arm

Differential Revision: https://reviews.llvm.org/D107807