km: qrio: fix set_gpio read/modify/write

km: qrio: fix set_gpio read/modify/write

Setting GPIO by reading the value of the GPRT register, toggling the
correct bit and then writing it causes input values to transfer to the
output. Here's how (example):

1) set gpio 17 and 18 as input.
2) set gpio 17 output value to 0 (read gprt, change 17 to 0, write).
3) set gpio 18 output value to 0 (read gprt, change 18 to 0, write).

The problem here is that because we set 17 as input, and it's a pull-up,
when we read gprt in step 3, the bit 17 will be 1 and not 0.
Instead of doing read/write/modify, the solution is to keep track
internally of the user set GPIOs, and replace the read step with this
static variable.

Signed-off-by: Tomas Alvarez Vanoli <tomas.alvarez-vanoli@hitachienergy.com>
Signed-off-by: Holger Brunck <holger.brunck@hitachienergy.com>