The ARMv7 architecture deprecates the separate Instruction and Data TLB

The ARMv7 architecture deprecates the separate Instruction and Data TLB
maintanenance instruction and recommends to only use the instructions that
operate on the unified TLB.  Those instructions will flush both TLBs on
implementations that still have separate Instruction and Data TLBs.  Switch
the TLB maintenance primitives over to use those.  This allows us to reduce
the number of primitives on armv7.  We still keep separate "ID" and "D"
variants as we still have to flush the branch predictor when changing the
mappings of pages that contain instructions.

ok jsg@