wil6210: fix warning in system power management code

wil6210: fix warning in system power management code

Fix compilation warning where CONFIG_PM defined while
CONFIG_PM_SLEEP is not defined

Report follows:

tree:   git://github.com/kvalo/ath pending
head:   941145fc5e5afbb120271e5dfaf37213ddb55807
commit: df596be39294d9712e5d568063a48448031e0a9f [37/39] wil6210: system power management
config: xtensa-allyesconfig (attached as .config)
reproduce:
  wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
  chmod +x ~/bin/make.cross
  git checkout df596be39294d9712e5d568063a48448031e0a9f
  # save the attached .config to linux build tree
  make.cross ARCH=xtensa

All warnings (new ones prefixed by >>):

>> drivers/net/wireless/ath/wil6210/pcie_bus.c:264:12: warning: 'wil6210_suspend' defined but not used [-Wunused-function]
    static int wil6210_suspend(struct device *dev, bool is_runtime)
               ^
>> drivers/net/wireless/ath/wil6210/pcie_bus.c:291:12: warning: 'wil6210_resume' defined but not used [-Wunused-function]
    static int wil6210_resume(struct device *dev, bool is_runtime)
               ^
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>