LoongArch: Add gas testsuit for alias instructions

Test the alias instructions.

gas/testsuite/gas/loongarch/insn_alias_32.d

@@ -0,0 +1,19 @@
+#as:
+#objdump: -d -M no-aliases
+#skip: loongarch64-*-*
+
+.*     file format .*
+
+
+Disassembly of section .text:
+
+0+ <L1>:
+   0:	001500a4 	or          	\$a0, \$a1, \$zero
+   4:	02bffc04 	addi.w      	\$a0, \$zero, -1
+   8:	03400000 	andi        	\$zero, \$zero, 0x0
+   c:	03800404 	ori         	\$a0, \$zero, 0x1
+  10:	4c000020 	jirl        	\$zero, \$ra, 0
+  14:	4c000020 	jirl        	\$zero, \$ra, 0
+  18:	60000080 	blt         	\$a0, \$zero, 0	# 18 <L1\+0x18>
+  1c:	64000080 	bge         	\$a0, \$zero, 0	# 1c <L1\+0x1c>
+  20:	64000004 	bge         	\$zero, \$a0, 0	# 20 <L1\+0x20>

gas/testsuite/gas/loongarch/insn_alias_32.s

@@ -0,0 +1,10 @@
+L1:
+  move  $a0,$a1
+  li.w  $a0,-1
+  nop
+  li.w	$a0,1
+  ret
+  jr    $ra
+  bltz  $a0,.L1
+  bgez  $a0,.L1
+  blez  $a0,.L1

gas/testsuite/gas/loongarch/insn_alias_64.d

@@ -0,0 +1,20 @@
+#as-new:
+#objdump: -d -M no-aliases
+#skip: loongarch32-*-*
+
+.*:     file format .*
+
+
+Disassembly of section .text:
+
+0+ <L1>:
+   0:	001500a4 	or          	\$a0, \$a1, \$zero
+   4:	02bffc04 	addi.w      	\$a0, \$zero, -1
+   8:	02bffc04 	addi.w      	\$a0, \$zero, -1
+   c:	03400000 	andi        	\$zero, \$zero, 0x0
+  10:	03800404 	ori         	\$a0, \$zero, 0x1
+  14:	4c000020 	jirl        	\$zero, \$ra, 0
+  18:	4c000020 	jirl        	\$zero, \$ra, 0
+  1c:	60000080 	blt         	\$a0, \$zero, 0	# 1c <L1\+0x1c>
+  20:	64000080 	bge         	\$a0, \$zero, 0	# 20 <L1\+0x20>
+  24:	64000004 	bge         	\$zero, \$a0, 0	# 24 <L1\+0x24>

gas/testsuite/gas/loongarch/insn_alias_64.s

@@ -0,0 +1,11 @@
+L1:
+  move  $a0,$a1
+  li.w  $a0,-1
+  li.d  $a0,-1
+  nop
+  li.w	$a0,1
+  ret
+  jr    $ra
+  bltz  $a0,.L1
+  bgez  $a0,.L1
+  blez  $a0,.L1