fbcon: Set rotate_font callback with related callbacks

fbcon: Set rotate_font callback with related callbacks

The field struct fbcon_par.rotate_font points to fbcon_rotate_font() if
the console is rotated. Set the callback in the same place as the other
callbacks. Prepares for declaring all fbcon callbacks in a dedicated
struct type.

If not rotated, fbcon_set_bitops() still clears the callback to NULL.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://lore.kernel.org/r/20250909124616.143365-4-tzimmermann@suse.de