dma/Kconfig: Make TI_EDMA select TI_PRIV_EDMA

The TI_EDMA driver unconditionally calls functions provided by the
TI_PRIV_EDMA code, but it doesn't force that to be built-in.  If that isn't
otherwise enabled somewhere, you can get build errors like:

linux-3.12.0-0.rc0.git1.1.fc21.armv7hl/drivers/dma/edma.c:593: undefined reference to `edma_free_slot'
drivers/built-in.o: In function `edma_terminate_all':
linux-3.12.0-0.rc0.git1.1.fc21.armv7hl/drivers/dma/edma.c:169: undefined reference to `edma_stop'
drivers/built-in.o: In function `edma_execute':
linux-3.12.0-0.rc0.git1.1.fc21.armv7hl/drivers/dma/edma.c:122: undefined reference to `edma_write_slot'
linux-3.12.0-0.rc0.git1.1.fc21.armv7hl/drivers/dma/edma.c:149: undefined reference to `edma_link'
linux-3.12.0-0.rc0.git1.1.fc21.armv7hl/drivers/dma/edma.c:152: undefined reference to `edma_start'

Make TI_EDMA select TI_PRIV_EDMA to avoid this.

Signed-off-by: Josh Boyer <jwboyer@fedoraproject.org>
Acked-by: Matt Porter <matt.porter@linaro.org>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>