Fix gcc.target/aarch64/torture/simd-abi-8.c for big-endian

Fix a big-endian failure reported by Christophe.  Also tighten the
test so that it doesn't allow saving and restoring 128-bit vectors
as Q registers.

2019-10-04  Richard Sandiford  <richard.sandiford@arm.com>

gcc/testsuite/
	* gcc.target/aarch64/torture/simd-abi-8.c: Use -mlittle-endian.
	Check that there are no Q register saves or restores.

From-SVN: r276577

gcc/testsuite/ChangeLog

+2019-10-04  Richard Sandiford  <richard.sandiford@arm.com>
+
+	* gcc.target/aarch64/torture/simd-abi-8.c: Use -mlittle-endian.
+	Check that there are no Q register saves or restores.
+
 2019-10-04  Richard Biener  <rguenther@suse.de>
 
 	* gcc.c-torture/execute/loop-3.c: Fix undefined behavior.

gcc/testsuite/gcc.target/aarch64/torture/simd-abi-8.c

 /* { dg-do compile } */
-/* { dg-options "-std=gnu99" } */
+/* { dg-options "-std=gnu99 -mlittle-endian" } */
 /* { dg-skip-if "" { *-*-* } { "-O0" } { "" } } */
 
 #include <arm_neon.h>
@@ -18,3 +18,5 @@ g (int64x2x4_t *ptr)
 
 /* { dg-final { scan-assembler-times {\tld1\t} 1 } } */
 /* { dg-final { scan-assembler-times {\tst1\t} 1 } } */
+/* { dg-final { scan-assembler-not {\tld[pr]\tq} } } */
+/* { dg-final { scan-assembler-not {\tst[pr]\tq} } } */