drivers/video/console/newport_con.c: fix read outside array bounds

It reads linetable[] before checking bounds of index, and ARRAY_SIZE is
required because linetable[] are unsigned shorts.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>