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

asm/evex.go

@@ -701,7 +701,7 @@ func splitMask(ops []Operand) ([]Operand, int, error) {
 				return nil, 0, fmt.Errorf("at most one mask register operand")
 			}
 			if r.idx == 0 {
-				return nil, 0, fmt.Errorf("K0 is not a usable mask register")
+				return nil, 0, fmt.Errorf("k0 is not a usable mask register")
 			}
 			mask = r.idx
 			continue
@@ -1203,7 +1203,7 @@ func (e *enc) emitEvexFields(spec evexSpec, ll, regIdx, vvvvIdx int, rm Operand,
 	// The b bit and the L'L field carry the rounding/SAE/broadcast mode:
 	// a rounding mode replaces L'L with the rc value, plain SAE and
 	// broadcast keep the vector length.
-	b, ll := 0, ll
+	b := 0
 	switch {
 	case sfx.rounding >= 0:
 		b, ll = 1, sfx.rounding