Blackfin arch: add missing CONFIG_LARGE_ALLOCS when upstream merging

Signed-off-by: Bryan Wu <bryan.wu@analog.com>

arch/blackfin/Kconfig

@@ -585,6 +585,14 @@ endchoice
 
 source "mm/Kconfig"
 
+config LARGE_ALLOCS
+	bool "Allow allocating large blocks (> 1MB) of memory"
+	help
+	  Allow the slab memory allocator to keep chains for very large
+	  memory sizes - upto 32MB. You may need this if your system has
+	  a lot of RAM, and you need to able to allocate very large
+	  contiguous chunks. If unsure, say N.
+
 config BFIN_DMA_5XX
 	bool "Enable DMA Support"
 	depends on (BF533 || BF532 || BF531 || BF537 || BF536 || BF534 || BF561 || BF54x)