CONFIG_PPC_FPU is not available for thedefaultarchitecture x86.
Result is shown for architecture powerpc

Support for Floating Point Unit (FPU)

modulename: ldstfp.ko

configname: CONFIG_PPC_FPU

Linux Kernel Configuration
└─>Processor support
└─>Support for Floating Point Unit (FPU)
In linux kernel since version 2.6.15 (release Date: 2006-01-02)  
This must be enabled to support the Floating Point Unit
Most 6xx have an FPU but e300c2 core (mpc832x) don't have
an FPU, so when building an embedded kernel for that target
you can disable FPU support.

If unsure say Y.

source code: