Saves on 10's of complains about 'defined but not used' variables.

Fixes the following W=1 kernel build warning(s):

 In file included from drivers/net/wireless/marvell/mwifiex/main.h:57,
 from drivers/net/wireless/marvell/mwifiex/main.c:22:
 drivers/net/wireless/marvell/mwifiex/pcie.h:310:41: warning: ‘mwifiex_pcie8997’ defined but not used [-Wunused-const-variable=]
 310 | static const struct mwifiex_pcie_device mwifiex_pcie8997 = {
 | ^~~~~~~~~~~~~~~~
 drivers/net/wireless/marvell/mwifiex/pcie.h:300:41: warning: ‘mwifiex_pcie8897’ defined but not used [-Wunused-const-variable=]
 300 | static const struct mwifiex_pcie_device mwifiex_pcie8897 = {
 | ^~~~~~~~~~~~~~~~
 drivers/net/wireless/marvell/mwifiex/pcie.h:292:41: warning: ‘mwifiex_pcie8766’ defined but not used [-Wunused-const-variable=]
 292 | static const struct mwifiex_pcie_device mwifiex_pcie8766 = {
 | ^~~~~~~~~~~~~~~~

 NB: Repeats 10's of times - snipped for brevity.

Cc: Amitkumar Karwar <amitkarwar@gmail.com>
Cc: Ganapathi Bhat <ganapathi.bhat@nxp.com>
Cc: Xinming Hu <huxinming820@gmail.com>
Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: linux-wireless@vger.kernel.org
Cc: netdev@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200826093401.1458456-2-lee.jones@linaro.org