Do not define IN_MODULE.  The IS_IN framework will define it for us.
This fixes a macro redefinition warning.

rtkaio is not upstream, so there is no upstream patch.

diff --git a/rtkaio/Makefile b/rtkaio/Makefile
index 066a1232e1bae283..cf42e0cbbdf04134 100644
--- a/rtkaio/Makefile
+++ b/rtkaio/Makefile
@@ -69,7 +69,7 @@ CFLAGS-kaio_librt-cancellation.c = -fasynchronous-unwind-tables
 
 LDFLAGS-rtkaio.so = -Wl,-soname=lib$(libprefix)rt.so$(librt.so-version) \
 		    -Wl,--enable-new-dtags,-z,nodelete
-CPPFLAGS-librtkaio += -UIN_MODULE -DIN_MODULE=MODULE_librt \
+CPPFLAGS-librtkaio += \
 		      -UMODULE_NAME -DMODULE_NAME=librt \
 		      -UIS_IN_librt -DIS_IN_librt=1 \
 		      -I$(..)rt