fix cleanup of redundant returns

The cleanup step for removing redundant returns at the end of void
functions (added in commit 49c0bf4a) was flawed. Redundant returns have
a space (ie. 'return ;'), so adjust the regex to match that.

cleanup/cleanup.sh

@@ -78,7 +78,7 @@ sed -i 's|\(#define DBG1.*\)||g' tn40.h
 # early returns from block scope. It's ugly, but semantically-important
 # whitespace works for python and Lindent ensures that the indentation is
 # consistent here.
-sed -i 's|^\treturn;.*||g' *.c
+sed -i 's|^\treturn\s*;.*||g' *.c
 
 
 # remove unused FTRACE_ON and FTRACE_OFF macros