rtlwifi: rtl8192se: Remove set but not used variable 'seg_ptr'

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

drivers/net/wireless/realtek/rtlwifi/rtl8192se/fw.c: In function '_rtl92s_firmware_downloadcode':
drivers/net/wireless/realtek/rtlwifi/rtl8192se/fw.c:139:17: warning:
 variable 'seg_ptr' set but not used [-Wunused-but-set-variable]

It's not used after commit 59ae1d12

 ("networking: introduce and use
skb_put_data()")

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