[coreboot] [PATCH] Remove warnings

[Myles Watson]

These three patches get rid of a few more warnings for me.

abuild tested.

Signed-off-by: Myles Watson

PS.  It looks like part of the reason we have so many warnings is the misuse
of #define __ROMCC__ to mean "early code before the device tree is
available"  __ROMCC__ is also used to get rid of prototypes because romcc
doesn't support them.  What's the right thing to do here?  Maybe we should
split the meanings so that we test for __GNUC__ when we mean "not romcc",
and we test for __ROMCC__ (renamed, of course, later) when we mean early
init?

Thanks,
Myles