gdb: step debug init runtc readelf missin -s

Author: cirosantilli

README.adoc

@@ -1845,7 +1845,7 @@ We have also double checked the address with:
 
 ....
 ./runtc -a arm readelf \
-  ./out/arm/buildroot/build/kernel_module-1.0/user/hello.out | \
+  -s ./out/arm/buildroot/build/kernel_module-1.0/user/hello.out | \
   grep main
 ....