[AArch64] Remove unused commutative attribute

The commutative attribute was once used by the SVE conditional binary
expanders, but it's now dead code.

2019-08-07  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* config/aarch64/iterators.md (commutative): Remove.

From-SVN: r274182

gcc/ChangeLog

+2019-08-07  Richard Sandiford  <richard.sandiford@arm.com>
+
+	* config/aarch64/iterators.md (commutative): Remove.
+
 2019-08-07  Richard Earnshaw  <rearnsha@arm.com>
 
 	PR driver/91130

gcc/config/aarch64/iterators.md

@@ -1925,10 +1925,3 @@
 			      (UNSPEC_COND_FMLS "fmsb")
 			      (UNSPEC_COND_FNMLA "fnmad")
 			      (UNSPEC_COND_FNMLS "fnmsb")])
-
-(define_int_attr commutative [(UNSPEC_COND_ADD "true")
-			      (UNSPEC_COND_SUB "false")
-			      (UNSPEC_COND_MUL "true")
-			      (UNSPEC_COND_DIV "false")
-			      (UNSPEC_COND_MIN "true")
-			      (UNSPEC_COND_MAX "true")])