libc: Fix l64a to return the correct buffer pointer

l64a was returning the pointer to the end of the internal
buffer instead of the start. This caused an infinite loop
in passwd application.

Signed-off-by: Filippo Arcidiacono <filippo.arcidiacono@st.com>
Signed-off-by: Carmelo Amoroso <carmelo.amoroso@st.com>

libc/stdlib/l64a.c

@@ -52,5 +52,5 @@ char * l64a (long int n)
     }
   *p = '\0';
 
-  return p;
+  return result;
 }