spi: add new SoC mt8186 support for spi-mtk-nor

Merge series from guochun.mao@mediatek.com <guochun.mao@mediatek.com>:

These patches is mainly for adding mt8186 support.
The spi nor controller of mt8186 has some differences,
it needs one more clk, axi_s, for dma feature.
And also needs one extra dummy bit when read flash registers.