clk: mediatek: organize infrasys functions

clk: mediatek: organize infrasys functions

Move all infrasys ops and related functions next to each other in the
file for better organization.

Generally all ops functions are grouped together like this for the other
ops types (apmixedsys, topckgen, etc). However the infrasys functions
were mixed in with the other sections making them harder to find. This
will also give a logical place to add any future infrasys-specific
functions.

Signed-off-by: David Lechner <dlechner@baylibre.com>