add LE encoding test

Author: lei137

llvm/test/MC/PowerPC/ppc-encoding-ISAFuture.s

@@ -410,10 +410,14 @@
            paddis 10, 12, 1000000000, 0
 #CHECK-BE: paddis 10, 12, 1000000000, 0   # encoding: [0x06,0x00,0x3b,0x9a,
 #CHECK-BE-SAME:                                        0x3d,0x4c,0xca,0x00]
+#CHECK-LE: paddis 10, 12, 1000000000, 0   # encoding: [0x9a,0x3b,0x00,0x06,
+#CHECK-LE-SAME:                                        0x00,0xca,0x4c,0x3d]
 
            paddis 10, 0, 1000000000, 1
 #CHECK-BE: paddis 10, 0, 1000000000, 1    # encoding: [0x06,0x10,0x3b,0x9a,
 #CHECK-BE-SAME:                                        0x3d,0x40,0xca,0x00]
+#CHECK-LE: paddis 10, 0, 1000000000, 1    # encoding: [0x9a,0x3b,0x10,0x06,
+#CHECK-LE-SAME:                                        0x00,0xca,0x40,0x3d]
 
            xxmulmul 8, 3, 4, 2
 #CHECK-BE: xxmulmul 8, 3, 4, 2          # encoding: [0xed,0x03,0x22,0x08]