CONFIG_MCA is not available for thedefaultarchitecture x86.
Result is shown for architecture i386

MCA support

modulename: mca.ko

configname: CONFIG_MCA

Linux Kernel Configuration
└─>Bus options (PCI, PCMCIA, EISA, MCA, ISA)
└─>MCA support
In linux kernel since version 2.6.12  
MicroChannel Architecture is found in some IBM PS/2 machines and
laptops. It is a bus system similar to PCI or ISA. See
Documentation/mca.txt (and especially the web page given
there) before attempting to build an MCA bus kernel.