s390/sclp_early: Get rid of sclp_early_read_info_sccb_valid

The early sclp detect functions gather the available SCLP facility
information. The sclp_early_read_info_sccb_valid indicates whether the
early sclp request was valid.  However, one external reference to it
checks for particular sclp facility bits and this should be sufficient.
Another occurance is in the sclp_get_ipl_info() function that is called
later.  Because all information are available at the early stage, save
the ipl information when detecting the sclp facilities.  Hence, no more
checks for sclp_early_read_info_sccb_valid are required.

Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Reviewed-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>