[AArch64] [Obvious] Correct pattern target requirement

Had mistakenly used a target macro that was not defined and not the
relevant one instead of the macro that should be used.

TARGET_ARMV8_6 is not defined, and also not the macro we want to check.
Instead check TARGET_F64MM.

gcc/ChangeLog:

2020-01-17  Matthew Malcomson  <matthew.malcomson@arm.com>

	* config/aarch64/aarch64-sve.md (@aarch64_sve_ld1ro<mode>): Use
	the correct target macro.

gcc/ChangeLog

 2020-01-17  Matthew Malcomson  <matthew.malcomson@arm.com>
 
+	* config/aarch64/aarch64-sve.md (@aarch64_sve_ld1ro<mode>): Use the
+	correct target macro.
+
+2020-01-17  Matthew Malcomson  <matthew.malcomson@arm.com>
+
 	* config/aarch64/aarch64-protos.h
 	(aarch64_sve_ld1ro_operand_p): New.
 	* config/aarch64/aarch64-sve-builtins-base.cc

gcc/config/aarch64/aarch64-sve.md

@@ -2502,7 +2502,7 @@
 	   (match_operand:OI 1 "aarch64_sve_ld1ro_operand_<Vesize>"
 			       "UO<Vesize>")]
 	  UNSPEC_LD1RO))]
-  "TARGET_SVE && TARGET_ARMV8_6"
+  "TARGET_SVE && TARGET_F64MM"
   {
     operands[1] = gen_rtx_MEM (<VEL>mode, XEXP (operands[1], 0));
     return "ld1ro<Vesize>\t%0.<Vetype>, %2/z, %1";