CONFIG_ROMVECSIZE is not available for thedefaultarchitecture x86.
Result is shown for architecture m68k
default or selected kernelversion does not have config value CONFIG_ROMVECSIZE.
Result is shown for kernelversion 6.2.5

Size of ROM vector region (in bytes)


Linux Kernel Configuration
└─>Size of ROM vector region (in bytes)
In linux kernel since version 2.6.18 (release Date: 2006-09-19)  
Define the size of the vector region in ROM. For most 68000
variants this would be 0x400 bytes in size. Set to 0 if you do
not want a vector region at the start of the ROM.