net: txgbe: Fix memleak in txgbe_calc_eeprom_checksum()

eeprom_ptrs should be freed before returned.

Fixes: 049fe536 ("net: txgbe: Add operations to interact with firmware")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>