CONFIG_VCO_MULT is not available for thedefaultarchitecture x86.
Result is shown for architecture blackfin
default or selected kernelversion does not have config value CONFIG_VCO_MULT.
Result is shown for kernelversion 6.7-rc3

VCO Multiplier

configname: CONFIG_VCO_MULT

Linux Kernel Configuration
└─>Blackfin Processor Options
└─>Board customizations
└─>VCO Multiplier
In linux kernel since version 2.6.24 (release Date: 2008-01-24)  
This controls the frequency of the on-chip PLL. This can be between 1 and 64.
PLL Frequency = (Crystal Frequency) * (this setting)