[sve][acle] Add some C intrinsics for brain float types.

[sve][acle] Add some C intrinsics for brain float types.

Summary:
The following intrinsics has been added:

svuint16_t svcnt[_bf16]_m(svuint16_t inactive, svbool_t pg, svbfloat16_t op)
svuint16_t svcnt[_bf16]_x(svbool_t pg, svbfloat16_t op)
svuint16_t svcnt[_bf16]_z(svbool_t pg, svbfloat16_t op)

svbfloat16_t svtbl[_bf16](svbfloat16_t data, svuint16_t indices)

svbfloat16_t svtbl2[_bf16](svbfloat16x2_t data, svuint16_t indices)

svbfloat16_t svtbx[_bf16](svbfloat16_t fallback, svbfloat16_t data, svuint16_t indices)

Reviewers: c-rhodes, kmclaughlin, efriedma, sdesmalen, ctetreau

Subscribers: tschuett, hiraditya, rkruppe, psnobl, cfe-commits, llvm-commits

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D82429