ARM: dma-mapping: remove init_consistent_dma_size() stub

Since commit e9da6e9905e639b0 ("ARM: dma-mapping: remove custom consistent
dma region") setting consistent dma memory size is not longer required. All
calls to this function has been already removed, so the
init_consistent_dma_size() stub can also be gone.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>