hexagon: use the generic global coherent pool

Switch hexagon to use the generic code for dma_alloc_coherent from
a global pre-filled pool.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Cain <bcain@codeaurora.org>
diff --git a/arch/hexagon/Kconfig b/arch/hexagon/Kconfig
index e5a8520..aab1a40 100644
--- a/arch/hexagon/Kconfig
+++ b/arch/hexagon/Kconfig
@@ -7,6 +7,7 @@
 	select ARCH_32BIT_OFF_T
 	select ARCH_HAS_SYNC_DMA_FOR_DEVICE
 	select ARCH_NO_PREEMPT
+	select DMA_GLOBAL_POOL
 	# Other pending projects/to-do items.
 	# select HAVE_REGS_AND_STACK_ACCESS_API
 	# select HAVE_HW_BREAKPOINT if PERF_EVENTS