MIPS: Pistachio: Remove plat_setup_iocoherency

The Pistachio SoC does not have an IOCU.  Hence, DMA is non-coherent.

Remove the function checking for iocoherency and select
CONFIG_DMA_NONCOHERENT in Kconfig

This code is probably accidentally inherited from Malta.

Signed-off-by: Zubair Lutfullah Kakakhel <Zubair.Kakakhel@imgtec.com>
Reviewed-by: James Hartley <james.hartley@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/13433/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/Kconfig

@@ -384,7 +384,7 @@ config MACH_PISTACHIO
 	select CLKSRC_MIPS_GIC
 	select COMMON_CLK
 	select CSRC_R4K
-	select DMA_MAYBE_COHERENT
+	select DMA_NONCOHERENT
 	select GPIOLIB
 	select IRQ_MIPS_CPU
 	select LIBFDT