mtd: denali: remove unnecessary parentheses

We should use parentheses only when they are necessary
or they really improve the readability.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>