It looks this code was based on analogous code for i.MX6, but there
that variable was being used as a part of following switch
statement. Since this is not the case for i.MX7, just replace the
variable with direct function call.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>