dma-mapping: improve selection of dma_declare_coherent availability

This API is primarily used through DT entries, but two architectures
and two drivers call it directly.  So instead of selecting the config
symbol for random architectures pull it in implicitly for the actual
users.  Also rename the Kconfig option to describe the feature better.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Paul Burton <paul.burton@mips.com> # MIPS
Acked-by: Lee Jones <lee.jones@linaro.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/sh/Kconfig

@@ -7,11 +7,11 @@ config SUPERH
 	select ARCH_NO_COHERENT_DMA_MMAP if !MMU
 	select HAVE_PATA_PLATFORM
 	select CLKDEV_LOOKUP
+	select DMA_DECLARE_COHERENT
 	select HAVE_IDE if HAS_IOPORT_MAP
 	select HAVE_MEMBLOCK_NODE_MAP
 	select ARCH_DISCARD_MEMBLOCK
 	select HAVE_OPROFILE
-	select HAVE_GENERIC_DMA_COHERENT
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_PERF_EVENTS
 	select HAVE_DEBUG_BUGVERBOSE