[][kernel][common][eth][Fix Coverity scan warning]

[Description]
Fix Coverity scan warning.
    - Fix uninitialized variables in mtk_gmac_xgmii_path_setup().
    - Fix uninitialized variables in mt7621_gmac0_rgmii_adjust().
    - Fix uninitialized variables in mtk_mac_config().
    - Fix uninitialized variables in mtk_sgmii_setup_phya_gen1().
    - Fix uninitialized variables in mtk_sgmii_setup_mode_force().
    - Fix uninitialized variables in mtk_sgmii_restart_an().
    - Fix error handling for wait_for_completion_timeout().

[Release-log]
N/A


Change-Id: I86f36fa33efffb93dadbdedef51d44efb04fdb9a
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/6858102
3 files changed