Set the 'FR' bit in the status register for N32 kernels.

[jhb]

Summary

This permits N32 hard-float binaries to use 64-bit floating point
registers (which is what N32 binaries expect) matching the N64 ABI.

Test Plan

• boot a mipsn32hf world under qemu

[imp]

[jmallett]

This seems acceptable and correct within what's currently present. I feel like a unified macro for these sets of flags is really needed, to simplify the code and ensure consistency in checks, but as an incremental improvement this looks good. Thanks!