Move reset_n to LPC PIO0_4, a true open-drain pin

Move reset_n to LPC PIO0_4, a true open-drain pin

There are two pins on the LPC which operate in true open-drain mode,
PIO0_4 and PIO0_5. Use one of these instead of one of the 'pseudo open
drain' pins to make sure reset works correctly.

Signed-off-by: Keith Packard <keithp@keithp.com>