CONFIG_ARCH_BCM_MOBILE_SMP is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

CONFIG_ARCH_BCM_MOBILE_SMP (not configurable)

modulename: platsmp.ko


Linux Kernel Configuration
└─>Broadcom SoC Support
In linux kernel since version 3.10 (release Date: 2013-06-30)  
SMP support for the BCM281XX, BCM21664 and BCM23550 SoC families.
Provided as an option so SMP support for SoCs of this type
can be disabled for an SMP-enabled kernel.

source code: