net: txgbe: remove unused buffer in txgbe_calc_eeprom_checksum

net: txgbe: remove unused buffer in txgbe_calc_eeprom_checksum

Half a year passed since commit 049fe5365324c ("net: txgbe: Add operations
to interact with firmware") was submitted, the buffer in
txgbe_calc_eeprom_checksum was not used. So remove it and the related
branch codes.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202306200242.FXsHokaJ-lkp@intel.com/
Reviewed-by: Jiawen Wu <jiawenwu@trustnetic.com>
Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Link: https://lore.kernel.org/r/20230620062519.1575298-1-shaozhengchao@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>