This patch adds the appropriate macros, tests and codec entries to encode the following variants:
BFCVT <Hd>, <Sn>
BFCVTN <Vd>.4H, <Vn>.4S
BFCVTN2 <Vd>.8H, <Vn>.4S
BFDOT <Vd>.<Ts>, <Vn>.<Tb>, <Vm>.<Tb>
BFDOT <Vd>.<Ts>, <Vn>.<Tb>, <Vm>.2H[<index>]
BFMLALB <Vd>.4S, <Vn>.8H, <Vm>.8H
BFMLALB <Vd>.4S, <Vn>.8H, <Vm>.H[<index>]
BFMLALT <Vd>.4S, <Vn>.8H, <Vm>.8H
BFMLALT <Vd>.4S, <Vn>.8H, <Vm>.H[<index>]
BFMMLA <Vd>.4S, <Vn>.8H, <Vm>.8H
Issue #2626