net: dsa: qca8k: replace legacy gpio include

This patch replaces the legacy bulk gpio.h include
with the proper gpio/consumer.h variant. This was
caught by the kbuild test robot that was running
into an error because of this.

For more information why linux/gpio.h is bad can be found in:
commit 56a46b61

 ("gpio: Clarify that <linux/gpio.h> is legacy")

Reported-by: kbuild test robot <lkp@intel.com>
Link: https://www.spinics.net/lists/netdev/msg584447.html
Fixes: a653f2f5

 ("net: dsa: qca8k: introduce reset via gpio feature")
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
Reviewed-by: Vivien Didelot <vivien.didelot@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>