s390/sclp: remove unused sclp_early_printk_forced

This reverts commit 55a5542a ("s390/hibernate: fix error handling when
suspend cpu != resume cpu"). It added sclp_early_printk_force() which
is no longer used since commit 39421627 ("s390: remove broken
hibernate / power management support"). No hibernate - no problem.

Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>