s390/boot: Remove alt_stfle_fac_list from decompressor

It is nowhere used in the decompressor, therefore remove it.

Fixes: 17e89e13 ("s390/facilities: move stfl information from lowcore to global data")
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>