OMAPDSS: HDMI: Remove __exit macro from hdmi_uninit_display

This function is now used in the driver init path to handle
probe errors properly. Thus, it may be possible to use this function
outside the exit path.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Reported-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Signed-off-by: Ricardo Neri <ricardo.neri@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>