[][Fix ethernet bring up issue for MT7622]

[Description]
Fix ethernet bring up issue for MT7622

1. Add condition check before registering FE Interrupt.
2. Add condition check before accessing SGMII.
3. Bypass DMA monitor for NETSYSv1.

[Release-log]
N/A

Change-Id: Ie3327b879db03da9703c128ce77260705e12785e
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/6006420
2 files changed