cmd/link: stop requiring the math package on ARM

It was needed for the old softfloat implementation, which has
long gone.

Change-Id: Ib8d53689209a3b003d62f84c7c6047d8ec5df859
Reviewed-on: https://go-review.googlesource.com/c/go/+/220719
Reviewed-by: Than McIntosh <[email protected]>

Author: cherrymui

src/cmd/link/internal/ld/lib.go

@@ -409,9 +409,6 @@ func (ctxt *Link) loadlib() {
 	}
 
 	// load internal packages, if not already
-	if ctxt.Arch.Family == sys.ARM {
-		loadinternal(ctxt, "math")
-	}
 	if *flagRace {
 		loadinternal(ctxt, "runtime/race")
 	}