Move the generic arm memcmp.S into the generic directory.

Change-Id: I48e4d14a0dcddbb246edbac6d0329619574ab44d
diff --git a/libc/arch-arm/generic/generic.mk b/libc/arch-arm/generic/generic.mk
index 95be867..96ed949 100644
--- a/libc/arch-arm/generic/generic.mk
+++ b/libc/arch-arm/generic/generic.mk
@@ -1,4 +1,5 @@
 libc_bionic_src_files_arm += \
+    arch-arm/generic/bionic/memcmp.S \
     arch-arm/generic/bionic/memcpy.S \
     arch-arm/generic/bionic/memset.S \
     arch-arm/generic/bionic/strcmp.S \