Faster float library for RISC-V Hazard3

[Panda381]

I created a faster float library for RISC-V Hazard3 core. Maybe it could be added to the SDK. The functions have a bit lower precision, but I think for a microcontroller the speed of the float functions is more important than the precision. Most of the time the inaccuracy is about 1 lowest bit of mantissa.
science functions: https://github.com/Panda381/PicoLibSDK/blob/main/_sdk/src/sdk_float_riscv_sci.S
templates of science functions in C: https://github.com/Panda381/PicoLibSDK/blob/main/_sdk/src/sdk_float_riscv_sci.c
other float functions: https://github.com/Panda381/PicoLibSDK/blob/main/_sdk/src/sdk_float_riscv.S

[kilograham]

cc @Wren6991