smex: clear freed section buffer pointer on error

On a read error the section reader freed the output buffer but left the
caller's pointer set, so a caller cleanup path could free it again.
Clear the pointer after freeing.

Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>

Author: lrgirdwo

smex/elf.c

@@ -514,6 +514,10 @@ int elf_read_section(const struct elf_module *module, const char *section_name,
 
 error:
 	free(*dst_buff);
+	/* clear the caller's pointer so a caller cleanup path (e.g. ldc.c's
+	 * "if (buffer) free(buffer)") does not free the same buffer again
+	 */
+	*dst_buff = NULL;
 	return ret;
 }