runtime: reuse common code between 32 and 64-bit RISC-V

src/runtime/arch_tinygoriscv64.go

@@ -2,8 +2,6 @@
 
 package runtime
 
-import "device/riscv"
-
 const GOARCH = "arm64" // riscv pretends to be arm
 
 // The bitness of the CPU (e.g. 8, 32, 64).
@@ -13,7 +11,3 @@ const TargetBits = 64
 func align(ptr uintptr) uintptr {
 	return (ptr + 7) &^ 7
 }
-
-func getCurrentStackPointer() uintptr {
-	return riscv.AsmFull("mv {}, sp", nil)
-}