staging: vt6656: Use ARRAY_SIZE instead of hardcoded size

Use ARRAY_SIZE to replace the hardcoded size so we will never have a
mismatch.

Signed-off-by: Oscar Carter <oscar.carter@gmx.com>
Link: https://lore.kernel.org/r/20200318174015.7515-1-oscar.carter@gmx.com


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