CPU: Set flex ratio to nominal TDP ratio in bootblock

CPUs with configurable TDP will run the TSC at the max non-turbo
ratio for the maximum TDP value, which can cause issues if another
TDP is desired.  To deal with this we set the flex ratio to the
nominal TDP ratio early in the boot and then configure the Soft
Reset Data registers so the PCH can tell the CPU what frequency
to run at after a reset.

This is done very early in the bootblock because it is necessary
to reset the system after setting a flex ratio.

The end result is that the TSC will now increment at the max
non-turbo frequency for the nominal TDP.

On some system with 1.8GHz CPU ensure that the kernel
detects the CPU speed as ~1800mhz rather than ~2300mhz:

> dmesg | grep "MHz processor"
[    0.004000] Detected 1795.801 MHz processor.

Change-Id: I8436dced9199003b6423186a2b041e3f7b84ab8c
Signed-off-by: Duncan Laurie <dlaurie@google.com>
Reviewed-on: http://review.coreboot.org/1329
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

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