CONFIG_MACH_SMDK2443 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

SMDK2443

configname: CONFIG_MACH_SMDK2443

Linux Kernel Configuration
└─>Samsung S3C24XX SoCs Support
└─>SMDK2443
In linux kernel since version 2.6.21 (release Date: 2007-04-25)  
Say Y here if you are using an SMDK2443