powerpc/QE: prepare QE PIO code for GPIO LIB support

- split and export __par_io_config_pin() out of par_io_config_pin(), so we
  could use the prefixed version with GPIO LIB API;
- rename struct port_regs to qe_pio_regs, and place it into qe.h;
- rename #define NUM_OF_PINS to QE_PIO_PINS, and place it into qe.h.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Acked-By: Timur Tabi <timur@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>