clk: meson: fix SET_PARM macro

parameter val is not enclosed in parenthesis which is buggy when given an
expression instead of a simple value

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Reviewed-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Michael Turquette <mturquette@baylibre.com>
Link: lkml.kernel.org/r/20170309104154.28295-2-jbrunet@baylibre.com