CONFIG_OMAP_MUX is not available for the selected architecture x86.
Result is shown for architecture arm

OMAP multiplexing support

configname: CONFIG_OMAP_MUX

Linux Kernel Configuration
└─>TI OMAP Implementations
└─>OMAP multiplexing support
In linux kernel since version 2.6.12 )
Pin multiplexing support for OMAP boards. If your bootloader
sets the multiplexing correctly, say N. Otherwise, or if unsure,
say Y.
depends
CONFIG_ARCH_OMAP |
| CONFIG_ARCH_OMAP1

is selected by
CONFIG_SND_OMAP_SOC_N810