CONFIG_MACH_E750 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Toshiba e750

configname: CONFIG_MACH_E750

Linux Kernel Configuration
└─>PXA2xx/PXA3xx-based
└─>Intel PXA2xx/PXA3xx Implementations
└─>Toshiba e750
In linux kernel since version 2.6.25 (release Date: 2008-04-16)  
Say Y here if you intend to run this kernel on a Toshiba
e750 family PDA.