Revert "page_pool: Track DMA-mapped pages and unmap them when destroying the pool"

This reverts commit 4f51fb0d which is
commit ee62ce7a upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: I1778b757059df295816de520022729e7ab7348a1
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>