of: dma: fix typos in generic dma binding definition

Some semicolons were left out in the examples.

The #dma-channels and #dma-requests properties have a prefix
that is, by convention, reserved for cell size properties.
Rename those properties to dma-channels and dma-requests.

Signed-off-by: Matt Porter <mporter@ti.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Jon Hunter <jon-hunter@ti.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>