[][dts: mt7986: update SPIM's max frequency to 52MHz]

[Description]
Change SPIM's max frequency to 52MHz

[Release-log]
N/A

Change-Id: I5897deaa868e60eb81c74cef79f6a52148ee8a81
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/5396035
6 files changed