fbdev: omapfb: Remove unused hdmi5_core_handle_irqs

hdmi5_core_handle_irqs() has been unused since
commit f5bab222 ("OMAPDSS: HDMI: Add OMAP5 HDMI support")

Remove it.

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Signed-off-by: Helge Deller <deller@gmx.de>