s390/pci: use builtin_misc_device macro to simplify the code

Use the builtin_misc_device macro to simplify the code, which is the same
as declaring with device_initcall().

Signed-off-by: Li Zetao <lizetao1@huawei.com>
Acked-by: Niklas Schnelle <schnelle@linux.ibm.com>
Link: https://lore.kernel.org/r/20230815080833.1103609-1-lizetao1@huawei.com
Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>