fix: restore iota blocks, asm --format flag and prose after the syntax pass

asm/loong64_encode.go

@@ -105,10 +105,10 @@ func loong64RegNum(name string) int {
 	}
 	// F0–F31, FCC0–FCC7, FCSR0–FCSR31.
 	if len(name) >= 4 && name[:4] == "FCSR" {
-		return loong64RegSpecial(name[4:], "FCSR", 31)
+		return loong64RegSpecial(name[4:], 31)
 	}
 	if len(name) >= 3 && name[:3] == "FCC" {
-		return loong64RegSpecial(name[3:], "FCC", 7)
+		return loong64RegSpecial(name[3:], 7)
 	}
 	if len(name) < 2 {
 		return -1
@@ -131,7 +131,7 @@ func loong64RegNum(name string) int {
 }
 
 // loong64RegSpecial parses a numbered FCC/FCSR register.
-func loong64RegSpecial(digits, prefix string, max int) int {
+func loong64RegSpecial(digits string, max int) int {
 	if digits == "" {
 		return -1
 	}