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

Loft

configname: CONFIG_MACH_LOFT

Linux Kernel Configuration
└─>Intel IXP4xx Implementation Options
└─>Loft
In linux kernel since version 2.6.21 (release Date: 2007-04-25)  
Say 'Y' here if you want your kernel to support the Giant
Shoulder Inc Loft board (a minor variation on the standard
Gateworks Avila Network Platform).