DMA: shdma: shdma_chan_filter() has to be in shdma-base.h

shdma_chan_filter() is a function, provided by the shdma-base.c module,
move its declaration to the appropriate header.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski+renesas@gmail.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>