[Fix warning OP-TEE#2] Define CFG_DRAM_BASE with UL macro

Use the newly defined UL macro.

Signed-off-by: Clement Faure <clement.faure@nxp.com>

Author: clementfaure

core/arch/arm/plat-imx/conf.mk

@@ -331,7 +331,7 @@ endif
 
 ifeq ($(filter y, $(CFG_MX7ULP)), y)
 CFG_INIT_CNTVOFF ?= y
-CFG_DRAM_BASE ?= (0x80000000 - 0x20000000)
+CFG_DRAM_BASE ?= UL(0x60000000)
 $(call force,CFG_IMX_LPUART,y)
 $(call force,CFG_BOOT_SECONDARY_REQUEST,n)
 endif