[codegen] change operand type from bool to iflag for isub borrow vari…

…ants

The type of the borrow operands for the borrow variants of the isub
instruction (isub_bin, isub_bout, isub_borrow) was bool for compatibility
reasons for isa/riscv. Since support for these instructions on RISC
architectures has been temporarily suspended, we can safely change the
type to iflags.

cranelift-codegen/meta/src/shared/instructions.rs

@@ -1866,8 +1866,8 @@ pub fn define(
     let y = &operand("y", iB);
     let c_in = &operand_doc("c_in", iflags, "Input carry flag");
     let c_out = &operand_doc("c_out", iflags, "Output carry flag");
-    let b_in = &operand_doc("b_in", b1, "Input borrow flag");
-    let b_out = &operand_doc("b_out", b1, "Output borrow flag");
+    let b_in = &operand_doc("b_in", iflags, "Input borrow flag");
+    let b_out = &operand_doc("b_out", iflags, "Output borrow flag");
 
     ig.push(
         Inst::new(