ARM: OMAP2+: Drop unused sdma functions

We still have lots of legacy code for sdma, but some of it is now unused.
To simplify phasing out the old legacy sdma code, let's first remove all
currently unused functions:

omap_enable_dma_irq
omap_set_dma_write_mode
omap_set_dma_params
omap_dma_link_lch
omap_set_dma_callback
omap_dma_set_global_params

And with this, omap_dma_set_global_params now becomes static.

Cc: Aaro Koskinen <aaro.koskinen@iki.fi>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Peter Ujfalusi <peter.ujfalusi@ti.com>
Cc: Russell King <rmk+kernel@armlinux.org.uk>
Cc: Vinod Koul <vkoul@kernel.org>
Acked-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Tested-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>