Add NVMulSLFrm to represent "3-register multiply with scalar" operations and set

it as the format for the appropriate N3V*SL*<> classes.  These instructions
require special handling of the M:Vm field which encodes the restricted Dm and
the lane index within Dm.

Examples are A8.6.325 VMLA, VMLAL, VMLS, VMLSL (by scalar):

	vmlal.s32	q3, d2, d10[0]

llvm-svn: 99690