Commit e6046b5e ("MIPS: ralink: fix cpu clock of mt7621 and add dt
clk devices") includes a file that doesn't exist, causing build
failures... Revert it.

References: https://lore.kernel.org/linux-mips/CAJsYDVJvviz8a2oVmb0XL3OB+=Eecu-3kC9T9vsmxpuC_BqDSA@mail.gmail.com/Signed-off-by: Paul Burton <paul.burton@mips.com>