MIPS: BCM47XX: Fix clock detection for BCM5354 with 200MHz clock
Some BCM5354 SoCs are running at 200MHz, but it is not possible to read
the clock from a register like it is done on some other SoC in ssb and
bcma. These devices should have a clkfreq nvram configuration value set
to 200, read it and set the clock to the correct value.