amd-xgbe: Use int type to store negative error codes

Use int instead of unsigned int for the 'ret' variable to store return
values from functions that either return zero on success or negative error
codes on failure.  Storing negative error codes in an unsigned int causes
no runtime issues, but it's ugly as pants,  Change 'ret' from unsigned int
to int type - this change has no runtime impact.

Signed-off-by: Qianfeng Rong <rongqianfeng@vivo.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/20250826142159.525059-1-rongqianfeng@vivo.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>