colibri-vf: Disable pull-up configuration in GPIO pin mux

During very early boot-ROM execution the pinmux
configuration isi in Hi-Z state. If pull-up is enabled
on GPIO pad's there will be a short period of toggle
from high to low on the IO when GPIO is set low during
boot. To avoid this glitch, disable pull-up configuration
in GPIO pinmux.

Signed-off-by: Bhuvanchandra DV <bhuvanchandra.dv@toradex.com>