dmaengine: sh: Rework Kconfig and Makefile

Separate helpers and drivers in the Kconfig and Makefile to improve
readability and move the CONFIG_OF dependency from the Makefile to
Kconfig.

[pebolle@tiscali.nl: reported need to rename SHDMA_R8A73A4 instances]
Reported-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
[horms+renesas@verge.net.au: squashed rename of SHDMA_R8A73A4 instances]
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

drivers/dma/sh/shdma.h

@@ -62,7 +62,7 @@ struct sh_dmae_desc {
 #define to_sh_dev(chan) container_of(chan->shdma_chan.dma_chan.device,\
 				     struct sh_dmae_device, shdma_dev.dma_dev)
 
-#ifdef CONFIG_SHDMA_R8A73A4
+#ifdef CONFIG_SH_DMAE_R8A73A4
 extern const struct sh_dmae_pdata r8a73a4_dma_pdata;
 #define r8a73a4_shdma_devid (&r8a73a4_dma_pdata)
 #else