Blackfin: support smaller uncached DMA chunks for memory constrained systems

When working with 8 meg systems, forcing a 1 meg DMA chunk heavily cuts
into the available resources.  So support smaller chunks to better cover
needs for these systems.

Signed-off-by: Barry Song <barry.song@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/arch/blackfin/Kconfig b/arch/blackfin/Kconfig
index d703247..8141b1e 100644
--- a/arch/blackfin/Kconfig
+++ b/arch/blackfin/Kconfig
@@ -896,6 +896,12 @@
 	bool "Enable 2M DMA region"
 config DMA_UNCACHED_1M
 	bool "Enable 1M DMA region"
+config DMA_UNCACHED_512K
+	bool "Enable 512K DMA region"
+config DMA_UNCACHED_256K
+	bool "Enable 256K DMA region"
+config DMA_UNCACHED_128K
+	bool "Enable 128K DMA region"
 config DMA_UNCACHED_NONE
 	bool "Disable DMA region"
 endchoice