Revert "dma-mapping: add dma_opt_mapping_size()"

This reverts commit f3e7d947 which is
commit a229cc14 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: I11adbe3593133110b9d4a0994a0c8236fbc79e8e
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>