rtlwifi: rtl8723ae: remove unused variables

drivers/net/wireless/realtek/rtlwifi/rtl8723ae/dm.c:16:18:
 warning: ofdmswing_table defined but not used [-Wunused-const-variable=]
drivers/net/wireless/realtek/rtlwifi/rtl8723ae/dm.c:56:17:
 warning: cckswing_table_ch1ch13 defined but not used [-Wunused-const-variable=]
drivers/net/wireless/realtek/rtlwifi/rtl8723ae/dm.c:92:17:
 warning: cckswing_table_ch14 defined but not used [-Wunused-const-variable=]

These variable is never used, so remove them.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>