By allocating early memory for the firmware page tables, we
can write over the beginning of the initrd image.
So what we do now is:
1) Read in firmware translations table while still on the
firmware's trap table.
2) Switch to Linux trap table.
3) Init bootmem.
4) Build firmware page tables using __alloc_bootmem().
And this keeps the initrd from being clobbered.
Signed-off-by: David S. Miller <davem@davemloft.net>