Add rvfi_mode (set to constant 3 = M-mode)

Signed-off-by: Clifford Wolf <clifford@clifford.at>

picorv32.v

@@ -122,6 +122,7 @@ module picorv32 #(
 	output reg        rvfi_trap,
 	output reg        rvfi_halt,
 	output reg        rvfi_intr,
+	output reg [ 1:0] rvfi_mode,
 	output reg [ 4:0] rvfi_rs1_addr,
 	output reg [ 4:0] rvfi_rs2_addr,
 	output reg [31:0] rvfi_rs1_rdata,
@@ -1962,6 +1963,7 @@ module picorv32 #(
 		rvfi_trap <= trap;
 		rvfi_halt <= trap;
 		rvfi_intr <= dbg_irq_enter;
+		rvfi_mode <= 3;
 
 		if (!resetn) begin
 			dbg_irq_call <= 0;