riscv: Add DMA 64-bit address support

dma_addr_t holds any valid DMA address. If the DMA API only uses 32/64-bit
addresses, dma_addr_t need only be 32/64 bits wide.

Signed-off-by: Padmarao Begari <padmarao.begari@microchip.com>
Reviewed-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Bin Meng <bin.meng@windriver.com>
Reviewed-by: Rick Chen <rick@andestech.com>
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 30b0540..55eaee2 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -152,6 +152,10 @@
 config 64BIT
 	bool
 
+config DMA_ADDR_T_64BIT
+	bool
+	default y if 64BIT
+
 config SIFIVE_CLINT
 	bool
 	depends on RISCV_MMODE || SPL_RISCV_MMODE