clk: mediatek: mt7988: drop 1/1 infracfg spurious factor

Now that we can have advanced parent handling for mux, we can drop
spurious infracfg 1/1 factor. This is in preparation to make the clk
ID match the ID in upstream include for mt7988.

Drop the factor entry from mt7988-clk.h and reference to them in
mt7988.dtsi. Muxes and gates are updated to reference the topckgen clk
following how it's done in upstream kernel linux.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>