[coreboot] [PATCH]Make smp_write_bus private

[Patrick Georgi]

Hi,

with r6114, no board in trunk uses smp_write_bus directly anymore.
Instead, mptable_write_buses looks up all buses in the device tree and
adds them to the table accordingly.
I propose to hide smp_write_bus, so no new board can reintroduce such code.

==
Make smp_write_bus static (local scope), to prevent new boards from
using it directly again.

Signed-off-by: Patrick Georgi <[e-mail]