s390/ipl: add REIPL_CLEAR flag to os_info

Introduce new OS_INFO_FLAGS_ENTRY to os_info pointing to the field
with bit flags.
Add OS_INFO_FLAGS_ENTRY upon dump_reipl shutdown action processing and
set OS_INFO_FLAG_REIPL_CLEAR flag indicating 'clear' sysfs attribute has
been set on the panicked system for specified ipl type. This flag can be
used to inform the dumper whether LOAD_CLEAR or LOAD_NORMAL diag308
subcode to be used for ipl after dumping the memory.

Signed-off-by: Mikhail Zaslonko <zaslonko@linux.ibm.com>
Acked-by: Alexander Gordeev <agordeev@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>