tty/vt: consolemap: remove glyph < 0 check from set_inverse_trans_unicode()

glyph is now an int casted from u16. It can never be negative. So remove
the check and type glyph as u16 properly in set_inverse_trans_unicode().

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220607104946.18710-18-jslaby@suse.cz


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>