media: staging: atomisp: remove unused set_pd_base()

There's an implementation for set_pd_base at sh_mmu logic
with is said to be mandatory. However, the implementation
ends by calling a routine that does nothing.

So get rid of this entire nonsense.

Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>