[][regs: fix coverity errors]

[Description]
Fix a BAD_SHIFT error reported by coverity.

[Release-log]
N/A

Change-Id: I9555a03243fb7ff730c26eb55b136003ab2c1038
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/5415997
1 file changed