target/ppc: Get rid of POWERPC_MMU_VER() macros

target/ppc: Get rid of POWERPC_MMU_VER() macros

These macros were introduced to deal with the fact that the mmu_model
field has bit flags mixed in with what's otherwise an enum of various mmu
types.

We've now eliminated all those flags except for one, and that one -
POWERPC_MMU_64 - is already included/compared in the MMU_VER macros.  So,
we can get rid of those macros and just directly compare mmu_model values
in the places it was used.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Greg Kurz <groug@kaod.org>