Impact: cleanup, solve 80 columns wrap problems

mpc_config_bus should be renamed to mpc_bus.
The reason: the 'c' in MPC already means 'config' -
no need to repeat that in the type name.
Signed-off-by: NJaswinder Singh Rajput <jaswinderrajput@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>