Hexagon: adapt for dma_map_ops changes

Adapt core Hexagon architecture code for dma_map_ops changes: replace
alloc/free_coherent with generic alloc/free methods.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Richard Kuo <rkuo@codeaurora.org>