[coreboot] [PATCH] use memset

[Myles Watson]

I was having trouble with stack corruption.  Using memset (C) instead of
clear_memory(asm) speeds it up by almost a factor of 2 for a 1M region.

TSC difference with clear_memory 0xFA884D
TSC difference with memset 0x826742

Anyway, this patch removes a couple of files that don't need to exist
anymore, given that only K8 was using clear_memory.

SIgned-off-by: Myles Watson

Thanks,
Myles