staging: imx-drm: imx-hdmi: clean up hdmi_phy_wait_i2c_done

Simplify hdmi_phy_wait_i2c_done so the call to hdmi_readb is
only done in one place. Also check for timout before waiting
as suggested by Troy Kisky.
This also fixes a checkpatch warning.

Signed-off-by: Emil Renner Berthing <kernel@esmil.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>