auxdisplay: lcd2s: Use array size explicitly in lcd2s_gotoxy()

Currently the reading of the onstack array is confusing since two
out of three members are of different types. Let it be more clear
by explicitly set the array size, so everybody will understand that
parameters are cast to the type of the array.

While at it, add a missed space.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>