acpi: Quieten IASL output when 'make -s' is used

IASL compiler does not provide a command line option to turn off
its non-warning message. To quieten the output when 'make -s',
redirect its output to /dev/null.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
1 file changed