Check subreason to DiscInfo SWI and implement FreeOp 3
Detail: The DiscInfo SWI has already used 8 of the possible 9 return registers, so to reserve space for future information items, use R1 to specify a subreason. Update docs to reflect this and add previously omitted detail of the flag that is returned in R8. Add FreeOp 3. For solid state, non-removable discs on a PCIe interface we are a 'fast' FS. Without this FreeOp, the free/used bars are only updated when the Free window is opened instead of dynamically as files are modified. Admin: Based on a submission from Thomas Milius. Removed unused NVMeFS_SetLog from CmdHelp.