mm_drv: tlb: Fix mapped page in bank calculation

The initial implementation was broken during improvements.
There was incorrect assumption that all pages are unmapped at
initials state. In reality at the beginning whole memory is
powered on, so we should mark all pages as mapped. Later in
initialization code unused pages are unmapped and if after this
some banks become empty (all pages unmapped), the power is
switched off.

Signed-off-by: Jaroslaw Stelter <Jaroslaw.Stelter@intel.com>