glibc does not suppot single precision FPU configurations for ARCv3 targets

[kolerov]

I was refactoring support of ARCv3 in Buildroot and found out that glibc does not supporting single precision FPU configurations for ARCv3 targets. glibc assumes that all FPU registers are 64-bit registers, uses 64-bit FPU instructions only and adjusts __jmp_buf size for 64-bit FPU registers only.

Note that uClibc does not support FPU configurations at all.