fec: Include pinctrl header file

Commit 5bbde4d2 ("net: fec: use pinctrl PM helpers") caused the following
build error on m68k:

drivers/net/ethernet/freescale/fec_main.c: In function 'fec_enet_open':
drivers/net/ethernet/freescale/fec_main.c:1819:2: error: implicit declaration of function 'pinctrl_pm_select_default_state' [-Werror=implicit-function-declaration]
drivers/net/ethernet/freescale/fec_main.c: In function 'fec_enet_close':
drivers/net/ethernet/freescale/fec_main.c:1863:2: error: implicit declaration of function 'pinctrl_pm_select_sleep_state' [-Werror=implicit-function-declaration]

In order to fix the build error, include the linux/pinctrl/consumer.h header
file.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>