With the introduction of the PMAP_PREFER_{ALIGN,OFFSET} macros a long time ago,

With the introduction of the PMAP_PREFER_{ALIGN,OFFSET} macros a long time ago,
there are actually no more uses of the PMAP_PREFER() macro left in the kernel.
Remove that macro but keep PMAP_PREFER as a simple #define for it to let uvm
knows the PMAP_PREFER_{ALIGN,OFFSET} macros are available.

ok mpi@