[ARM,MVE] Remove 64-bit variants of vbrsrq* intrinsics

Summary:
According to the ACLE the vbrsrq* intrinsics don't accept vectors
with 64-bit elements (and neither does the corresponding VBRSR
instruction).

Reviewers: simon_tatham, dmgreen, MarkMurrayARM, ostannard

Reviewed By: simon_tatham

Subscribers: kristof.beyls, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D75038