rtlwifi: rtl8723: Remove set but not used variable 'own'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/net/wireless/realtek/rtlwifi/rtl8723com/fw_common.c: In function rtl8723_cmd_send_packet:
drivers/net/wireless/realtek/rtlwifi/rtl8723com/fw_common.c:226:5: warning: variable own set but not used [-Wunused-but-set-variable]

It is not used since commit f1d2b4d3 ("rtlwifi:
rtl818x: Move drivers into new realtek directory")

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: zhengbin <zhengbin13@huawei.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>