rockchip: rk3288-evb: update CONFIG_NR_DRAM_BANKS to 2

The OPTEE will use the ram start at 0x8400000 which make the DRAM be two
banks.
Signed-off-by: NKever Yang <kever.yang@rock-chips.com>

configs/evb-rk3288_defconfig

@@ -5,7 +5,7 @@ CONFIG_ROCKCHIP_RK3288=y
 CONFIG_TARGET_EVB_RK3288=y
 CONFIG_ENV_OFFSET=0x3F8000
 CONFIG_SPL_STACK_R_ADDR=0x04000000
-CONFIG_NR_DRAM_BANKS=1
+CONFIG_NR_DRAM_BANKS=2
 CONFIG_SPL_SIZE_LIMIT=0x4b000
 CONFIG_DEBUG_UART_BASE=0xff690000
 CONFIG_DEBUG_UART_CLOCK=24000000