s390/ipl: Fix incorrect initialization of nvme dump block

[ Upstream commit 7faacaea ]

Initialize the correct fields of the nvme dump block.
This bug had not been detected before because first, the fcp and nvme fields
of struct ipl_parameter_block are part of the same union and, therefore,
overlap in memory and second, they are identical in structure and size.

Fixes: d70e38cb ("s390: nvme dump support")
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>