Without explicitly enabling sel_clk, clk_disable_unused() will disable
it when boot is done, causing CPU hang on SPI1 register access on MT7986.
Explicitly enable sel_clk to make SPI1 functional.
Signed-off-by: Furong Xu <xfr@outlook.com>
Signed-off-by: Chuanhong Guo <gch981213@gmail.com>