VT: Bump font size limitation to 64x128 pixels

This moves 32x32 font size limitation checking down to drivers, so that
fbcon can allow large fonts.

We still keep a limitation to 64x128 pixels so as to have a simple bounded
allocation for con_font_get and in the userland kbd tool. That glyph size
will however be enough to have 128x36 characters on a "16/9 8K display".

Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Link: https://lore.kernel.org/r/20230119151935.112415738@ens-lyon.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>