Instead of having a fixed array of fonts register the fonts dynamically.
This allows easier adding of fonts to the tree since only one file per
font has to be added and no other files modified.

Currently we have to register the fonts very early before the first
framebuffer is registered. This is because of our limited
dev_add_param_enum() which wants to know the number of elements when
called, so we can't add elements once after we've called
dev_add_param_enum(). Maybe a dev_add_param_array() has to be created
whithout this limitation, but that's left for a future exercise.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>