prepared for 3 chains,
optimized out the led_bit_*() calls: 3+12 or 12+4
extended test script to show three different things on the three strings.
new module parameter gpios=11,12,18,19 as alternative to gpio_number and gpio_count
renamed led_chains to gpio_count.
kstrtol() cannot parse a list of numbers. Replaced with the usual one-liner.