drm: armada: use vblank hooks in struct drm_crtc_funcs

drm: armada: use vblank hooks in struct drm_crtc_funcs

The vblank hooks in struct drm_driver are deprecated and only meant for
legacy drivers.  For modern drivers with DRIVER_MODESET flag, the hooks
in struct drm_crtc_funcs should be used instead.  As the result,
functions armada_drm_crtc_enable[disable]_irq() can be static, although
they are moved around a bit to save forward declaration.

The armada_crtc pointer array in struct armada_private is still kept in
there, because armada_debugfs.c still have reference to it.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Cc: Russell King <linux@armlinux.org.uk>
Acked-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1486458995-31018-7-git-send-email-shawnguo@kernel.org