[sve][acle] Implement some of the C intrinsics for brain float.

Summary:
The following intrinsics have been extended to support brain float types:

svbfloat16_t svclasta[_bf16](svbool_t pg, svbfloat16_t fallback, svbfloat16_t data)
bfloat16_t svclasta[_n_bf16](svbool_t pg, bfloat16_t fallback, svbfloat16_t data)
bfloat16_t svlasta[_bf16](svbool_t pg, svbfloat16_t op)

svbfloat16_t svclastb[_bf16](svbool_t pg, svbfloat16_t fallback, svbfloat16_t data)
bfloat16_t svclastb[_n_bf16](svbool_t pg, bfloat16_t fallback, svbfloat16_t data)
bfloat16_t svlastb[_bf16](svbool_t pg, svbfloat16_t op)

svbfloat16_t svdup[_n]_bf16(bfloat16_t op)
svbfloat16_t svdup[_n]_bf16_m(svbfloat16_t inactive, svbool_t pg, bfloat16_t op)
svbfloat16_t svdup[_n]_bf16_x(svbool_t pg, bfloat16_t op)
svbfloat16_t svdup[_n]_bf16_z(svbool_t pg, bfloat16_t op)

svbfloat16_t svdupq[_n]_bf16(bfloat16_t x0, bfloat16_t x1, bfloat16_t x2, bfloat16_t x3, bfloat16_t x4, bfloat16_t x5, bfloat16_t x6, bfloat16_t x7)
svbfloat16_t svdupq_lane[_bf16](svbfloat16_t data, uint64_t index)

svbfloat16_t svinsr[_n_bf16](svbfloat16_t op1, bfloat16_t op2)

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

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

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D82345