[coreboot] [patch](trivial) Fix qemu target compilation with netconsole enabled

[Cristi Magherusan]

Hi,

See attached trivial patch.

This fix might apply to other boards that only have -mcpu=i386 set in
ROMCCFLAGS. Still, some won't work because of too large binaries that
won't fit the ROM size when enabling the netconsole.

Signed-off-by: Cristi Magherusan

Regards,
Cristi