wifi: rtw89: use int type to store negative error codes

wifi: rtw89: use int type to store negative error codes

The 'ret' variable stores returns from other functions, which return
either zero on success or negative error codes on failure.  Storing
error codes in u32 (an unsigned type) causes no runtime issues but is
stylistically inconsistent and very ugly.  Change 'ret' from u32 to
int - this has no runtime impact.

Signed-off-by: Qianfeng Rong <rongqianfeng@vivo.com>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20250827150620.550641-1-rongqianfeng@vivo.com