tty: serial: qcom_geni_serial: Clean up an ARRAY_SIZE() vs sizeof()

The ARRAY_SIZE() is the number of elements but we want the number of
bytes so sizeof() is more appropriate.  Fortunately, it's the same
thing here because this is an array of u8 so this doesn't change
runtime.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20200624132744.GD9972@mwanda


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