ARM: S3C64XX: Fix possible clock look in EPLL and MPLL clock chains

There is a possibility of a loop happening in the PLL output clock
chain on the S3C64XX series. clk_mpll's parent was set to be
clk_mout_mpll, but this is fed from clk_fout_epll (which is also
clk_mpll).

clk_mpll is meant to be the output from the MPLL, and clk_mout_mpll
is a seperate clock derived from the mux of clk_mpll and clk_fin_mpll
and thus should be considered a seperate clock.

Anything using clk_mpll directly really should not be relying on this
being the clock that is eventually routed to a peripheral, so remove the
loop and ensure that the clocks accurately represent the clock chain
in the device.

The clk_mpll is not being used outside of the s3c6400-clock.c code, so
this change should not break anything else.

Do the same for the EPLL.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>