Add back dummy free()

GNU CC coverage needs free() and it's highly desirable to leave
the code as genuine as possible.

Change-Id: I4c821b9d211ef7a8e7168dc5e3116730693999c6
Signed-off-by: Stefan Reinauer <reinauer@google.com>
Reviewed-on: http://review.coreboot.org/2051
Tested-by: build bot (Jenkins)
Reviewed-by: David Hendricks <dhendrix@chromium.org>

src/include/stdlib.h

@@ -14,6 +14,8 @@
 #if !defined(__PRE_RAM__)
 void *memalign(size_t boundary, size_t size);
 void *malloc(size_t size);
+/* We never free memory */
+static inline void free(void *ptr) {}
 #endif
 
 #endif /* STDLIB_H */