[RISCV] Remove unused SchedWrites WriteFConv32/WriteFConv64/WriteFMov32/WriteFMov64.

[craig.topper]

Summary

It doesn't look like any instructions have ever been assigned to these classes.

[HsiangKai]

LGTM.

llvm/lib/Target/RISCV/RISCVSchedule.td

 def WriteFCvtF32ToI64  : SchedWrite;    // RV64I only
 def WriteFCvtF64ToI32  : SchedWrite;
 def WriteFCvtF64ToI64  : SchedWrite;    // RV64I only
 
 // Float to float conversions
 def WriteFCvtF32ToF64  : SchedWrite;
 def WriteFCvtF64ToF32  : SchedWrite;
 
-def WriteFConv32    : SchedWrite;    // 32-bit floating point convert
-def WriteFConv64    : SchedWrite;    // 64-bit floating point convert
 def WriteFClass32   : SchedWrite;    // 32-bit floating point classify
 def WriteFClass64   : SchedWrite;    // 64-bit floating point classify
 def WriteFCmp32     : SchedWrite;    // 32-bit floating point compare
 def WriteFCmp64     : SchedWrite;    // 64-bit floating point compare
 def WriteFSGNJ32    : SchedWrite;    // 32-bit floating point sign-injection
 def WriteFSGNJ64    : SchedWrite;    // 64-bit floating point sign-injection
 def WriteFMinMax32  : SchedWrite;    // 32-bit floating point min or max
 def WriteFMinMax64  : SchedWrite;    // 64-bit floating point min or max
 
 def WriteFMovF32ToI32     : SchedWrite;
 def WriteFMovI32ToF32     : SchedWrite;
 def WriteFMovF64ToI64     : SchedWrite;    // RV64I only
 def WriteFMovI64ToF64     : SchedWrite;    // RV64I only
 
-def WriteFMov32       : SchedWrite;    // 32-bit floating point move
-def WriteFMov64       : SchedWrite;    // 64-bit floating point move
 def WriteFLD32        : SchedWrite;    // Floating point sp load
 def WriteFLD64        : SchedWrite;    // Floating point dp load
 def WriteFST32        : SchedWrite;    // Floating point sp store
 def WriteFST64        : SchedWrite;    // Floating point dp store
 
 /// Define scheduler resources associated with use operands.
 def ReadJmp         : SchedRead;
 def ReadJalr        : SchedRead;