s390/bug: Always emit format word in __BUG_ENTRY

When CONFIG_DEBUG_BUGVERBOSE is disabled, the s390 __BUG_ENTRY() macro
omits the format string pointer, so the generated __bug_table entry no
longer matches struct bug_entry.

With HAVE_ARCH_BUG_FORMAT enabled, the generic BUG infrastructure reads
bug_entry::format via bug_get_format(). If the format word is missing,
subsequent fields are read from the wrong offset, which may:
- Misinterpret flags (BUG vs WARN classification errors)
- Fault when dereferencing a misread format pointer

The root cause is that __BUG_ENTRY() delegates format word emission to
__BUG_ENTRY_VERBOSE(), which is conditional on CONFIG_DEBUG_BUGVERBOSE.

Fix this by moving the format field emission directly into __BUG_ENTRY()
so it is always emitted unconditionally. Remove the format parameter from
__BUG_ENTRY_VERBOSE() and keep only file/line emission conditional on
CONFIG_DEBUG_BUGVERBOSE.

Fixes: 2b71b8ab9718 ("s390/bug: Use BUG_FORMAT for DEBUG_BUGVERBOSE_DETAILED")
Signed-off-by: Jan Polensky <japo@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>