firmware: imx: scu-pd: use bool to set postfix

Using bool instead 0/1 to indicate whether adding a postfix for domain
names which can improve the code readability and less confusing.

Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <kernel@pengutronix.de>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Kevin Hilman <khilman@kernel.org>
Cc: linux-pm@vger.kernel.org
Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>