RISC-V: Update the assembler insn testcase.

Since the 0x57 is preserved for the vadd.vv instruction in the integration
branch, remove it to make sure the testcase can work.

gas/
	* testsuite/gas/riscv/insn.d: Remove 0x57 since it is preserved
	for vadd.vv instruction.
	* testsuite/gas/riscv/insn.s: Likewise.
diff --git a/gas/testsuite/gas/riscv/insn.d b/gas/testsuite/gas/riscv/insn.d
index 5b36107..e55030e 100644
--- a/gas/testsuite/gas/riscv/insn.d
+++ b/gas/testsuite/gas/riscv/insn.d
@@ -71,7 +71,5 @@
 [^:]+:[ 	]+00c58533[ 	]+add[ 	]+a0,a1,a2
 [^:]+:[ 	]+0001[ 	]+nop
 [^:]+:[ 	]+00000013[ 	]+nop
-[^:]+:[ 	]+00000057[ 	]+0x57
 [^:]+:[ 	]+0001[ 	]+nop
 [^:]+:[ 	]+00000013[ 	]+nop
-[^:]+:[ 	]+00000057[ 	]+0x57
diff --git a/gas/testsuite/gas/riscv/insn.s b/gas/testsuite/gas/riscv/insn.s
index 8473905..e47f529 100644
--- a/gas/testsuite/gas/riscv/insn.s
+++ b/gas/testsuite/gas/riscv/insn.s
@@ -56,7 +56,5 @@
 
 	.insn 0x0001
 	.insn 0x00000013
-	.insn 0x00000057
 	.insn 0x2, 0x0001
 	.insn 0x4, 0x00000013
-	.insn 0x4, 0x00000057