Kconfig: Rename CONFIG_SPL_DMA_SUPPORT to CONFIG_SPL_DMA

Rename CONFIG_SPL_DMA_SUPPORT to CONFIG_SPL_DMA. This allows to use
macros such as CONFIG_IS_ENABLED() that allow conditional compilation of
code for SPL and U-Boot.

Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/doc/README.SPL b/doc/README.SPL
index 3c931ec..929b967 100644
--- a/doc/README.SPL
+++ b/doc/README.SPL
@@ -59,7 +59,7 @@
 CONFIG_SPL_POWER_SUPPORT (drivers/power/libpower.o)
 CONFIG_SPL_NAND_SUPPORT (drivers/mtd/nand/raw/libnand.o)
 CONFIG_SPL_DRIVERS_MISC_SUPPORT (drivers/misc)
-CONFIG_SPL_DMA_SUPPORT (drivers/dma/libdma.o)
+CONFIG_SPL_DMA (drivers/dma/libdma.o)
 CONFIG_SPL_POST_MEM_SUPPORT (post/drivers/memory.o)
 CONFIG_SPL_NAND_LOAD (drivers/mtd/nand/raw/nand_spl_load.o)
 CONFIG_SPL_SPI_LOAD (drivers/mtd/spi/spi_spl_load.o)