MIPS: Remove DMA_PERDEV_COHERENT

As now we are always managing DMA coherence on per dev bias,
there is no need to have such option. And it's not selected
by any platform.
Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

arch/mips/Kconfig

@@ -1080,11 +1080,6 @@ config FW_CFE
 config ARCH_SUPPORTS_UPROBES
 	bool
 
-config DMA_PERDEV_COHERENT
-	bool
-	select ARCH_HAS_SETUP_DMA_OPS
-	select DMA_NONCOHERENT
-
 config DMA_NONCOHERENT
 	bool
 	#