[arm] Update FP16 tests

My recent assemble_real patch (r275873) meant that we now output
negative FP16 constants in the same way as we'd output an integer
subreg of them.  This patch updates gcc.target/arm/fp16-* accordingly.

2019-09-26  Richard Sandiford  <richard.sandiford@arm.com>

gcc/testsuite/
	* gcc.target/arm/fp16-compile-alt-3.c: Expect (__fp16) -2.0
	to be written as a negative short rather than a positive one.
	* gcc.target/arm/fp16-compile-ieee-3.c: Likewise.

From-SVN: r276145

gcc/testsuite/ChangeLog

+2019-09-26  Richard Sandiford  <richard.sandiford@arm.com>
+
+	* gcc.target/arm/fp16-compile-alt-3.c: Expect (__fp16) -2.0
+	to be written as a negative short rather than a positive one.
+	* gcc.target/arm/fp16-compile-ieee-3.c: Likewise.
+
 2019-09-26  Martin Liska  <mliska@suse.cz>
 
 	PR tree-optimization/91885

gcc/testsuite/gcc.target/arm/fp16-compile-alt-3.c

@@ -7,4 +7,4 @@
 __fp16 xx = -2.0;
 
 /* { dg-final { scan-assembler "\t.size\txx, 2" } } */
-/* { dg-final { scan-assembler "\t.short\t49152" } } */
+/* { dg-final { scan-assembler "\t.short\t-16384" } } */

gcc/testsuite/gcc.target/arm/fp16-compile-ieee-3.c

@@ -6,4 +6,4 @@
 __fp16 xx = -2.0;
 
 /* { dg-final { scan-assembler "\t.size\txx, 2" } } */
-/* { dg-final { scan-assembler "\t.short\t49152" } } */
+/* { dg-final { scan-assembler "\t.short\t-16384" } } */