Rename operand-aarch32.{h,cc} to operands-aarch32.{h,cc}

We were inconsistent in naming this file between the AArch64 and AArch32
targets, let's go with what AArch64 calls is and pluralize operand.

Change-Id: Id2581255e4aa398f2c6fa81e5abce1f4b9b8a364
diff --git a/src/aarch32/macro-assembler-aarch32.h b/src/aarch32/macro-assembler-aarch32.h
index 6fbcf28..5f6bf04 100644
--- a/src/aarch32/macro-assembler-aarch32.h
+++ b/src/aarch32/macro-assembler-aarch32.h
@@ -31,7 +31,7 @@
 #include "utils-vixl.h"
 #include "aarch32/instructions-aarch32.h"
 #include "aarch32/assembler-aarch32.h"
-#include "aarch32/operand-aarch32.h"
+#include "aarch32/operands-aarch32.h"
 
 namespace vixl {
 namespace aarch32 {