drivers: dma-removed: page align size on free

Fix removed ops memory leak which occurs when non-page
aligned memory is freed.

On free we need to page align the amount of memory being
freed otherwise we risk rounding down the size of the
allocation to the page boundary which would leak one page.

Change-Id: Idabce39cad526eeaf073748edb227b2edd76f40e
Signed-off-by: Liam Mark <lmark@codeaurora.org>