libm: ARM: reorganize a bit to match ARM64

* Cleaner naming, especially if there are more ARM-specific routines in
  the future.

Change-Id: Id29db728800ccd612a906e86ccb95c1e7620514d
diff --git a/libm/Android.mk b/libm/Android.mk
index 7a7e3b0..7b28f70 100644
--- a/libm/Android.mk
+++ b/libm/Android.mk
@@ -283,9 +283,8 @@
 
 else
 LOCAL_SRC_FILES_arm += \
-    arm/e_sqrt.S \
-    arm/e_sqrtf.S \
-    arm/s_floor.S \
+    arm/sqrt.S \
+    arm/floor.S \
 
 endif