net: txgbe: fix heap overflow when reading module EEPROM

net: txgbe: fix heap overflow when reading module EEPROM

txgbe_read_eeprom_hostif() always copies round_up(length, 4) bytes
into the caller buffer, which ethtool allocates with exactly 'length'
bytes. A non-4-aligned length therefore causes an out-of-bounds write.
Copy only the remaining bytes on the final dword instead.

Signed-off-by: Chenguang Zhao <zhaochenguang@kylinos.cn>
Reviewed-by: Jiawen Wu <jiawenwu@trustnetic.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Fixes: 9b97b6b5635b ("net: txgbe: support getting module EEPROM by page")
Link: https://patch.msgid.link/20260713085111.1481884-1-chenguang.zhao@linux.dev
Signed-off-by: Jakub Kicinski <kuba@kernel.org>