powerpc: Use new CPU feature bit to select 2.06 tlbie

This removes MMU_FTR_TLBIE_206 as we can now use CPU_FTR_HVMODE_206.  It
also changes the logic to select which tlbie to use to be based on this
new CPU feature bit.

This also duplicates the ASM_FTR_IF/SET/CLR defines for CPU features
(copied from MMU features).

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>