s390/sclp: Add check for get_zeroed_page()

In the Linux kernel, the following vulnerability has been resolved: s390/sclp: Add check for get_zeroed_page() Add check for the return value of get_zeroed_page() in sclp_console_init() to prevent null pointer dereference. Furthermore, to solve the memory leak caused by the loop allocation, add a free helper to do the free job.