Remove the gpio mux setup function from i.MX framebuffer driver.
This function is platform specific and thus should be done by
the board setup. As there are currently no in-kernel users
of this driver we do not break anything.
Acked-by: Krzysztof Helt <krzysztof.h1@poczta.fm>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>