dma-pool: decouple DMA_REMAP from DMA_COHERENT_POOL

DMA_REMAP is an unnecessary requirement for AMD SEV, which requires
DMA_COHERENT_POOL, so avoid selecting it when it is otherwise unnecessary.

The only other requirement for DMA coherent pools is DMA_DIRECT_REMAP, so
ensure that properly selects the config option when needed.

Fixes: 82fef0ad ("x86/mm: unencrypted non-blocking DMA allocations use coherent pools")
Reported-by: Alex Xu (Hello71) <alex_y_xu@yahoo.ca>
Signed-off-by: David Rientjes <rientjes@google.com>
Tested-by: Alex Xu (Hello71) <alex_y_xu@yahoo.ca>
Signed-off-by: Christoph Hellwig <hch@lst.de>

kernel/dma/Kconfig

@@ -73,18 +73,18 @@ config SWIOTLB
 config DMA_NONCOHERENT_MMAP
 	bool
 
+config DMA_COHERENT_POOL
+	bool
+
 config DMA_REMAP
+	bool
 	depends on MMU
 	select GENERIC_ALLOCATOR
 	select DMA_NONCOHERENT_MMAP
-	bool
-
-config DMA_COHERENT_POOL
-	bool
-	select DMA_REMAP
 
 config DMA_DIRECT_REMAP
 	bool
+	select DMA_REMAP
 	select DMA_COHERENT_POOL
 
 config DMA_CMA