CONFIG_PPC_SMP_MUXED_IPI is not available for thedefaultarchitecture x86.
Result is shown for architecture powerpc

CONFIG_PPC_SMP_MUXED_IPI (not configurable)

configname: CONFIG_PPC_SMP_MUXED_IPI

Linux Kernel Configuration
└─>Platform support
└─>PPC_SMP_MUXED_IPI
In linux kernel since version 3 (release Date: 2011-07-21)  
Select this opton if your platform supports SMP and your
interrupt controller provides less than 4 interrupts to each
cpu. This will enable the generic code to multiplex the 4
messages on to one ipi.

is depended by
CONFIG_PPC_ISERIES