[coreboot] T440P: Unable to initialize memory speeds above 1600 MT/s

I just bought a pair of HyperX DDR3L-2133 CL11 memory. They are supported and run fine at 2133 MT/s with the original Lenovo firmware.

However Coreboot only registers them at 1600 MT/s.

Changing the value of .max_ddr3_freq to 2133 in src/mainboard/lenovo/t440p/romstage.c leads to a bricked notebook. A beeping sound occurs, regardless of the installed memory type (1600 or 2133).