staging: mali: Kconfig: Enable MALI400 and MALI_DT as default

Enable MALI400 as default. the MALI DT support should be enabled as well
so that the Zynq / ZynqMP platform code (address, interrupt) doesn't
have to hardcoded in the driver.

Signed-off-by: Hyun Kwon <hyun.kwon@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>