We now have confirmation that it fixed the problem.

It's redundant with the new scheme, so just adds HW for no reason.

We were zero-extending it, which is a double-precision zero in the recoded
format.  So, when spilled and reloaded with fsd/fld, the original value
was destroyed.  Instead, set the MSBs so that it represents sNaN.  When
spilled, the single-precision number will be preserved as the NaN payload.

PeripheryExtInterrupts: elide node if NExtTopInterrupts = 0

Dts - Device Tree Output

This makes it possible for the PLIC to work with heterogenous cores.

Periphery adjustments

Make it easier to build riscv-tools faster on multicore machines

In particular, this bump allows chisel Records and firrtl Bundles to
have fields with names that start with a digit. Mainly effect is
removing the double '_' from trying to have digits as names in Records.