scsi: libfc: Replace one-element arrays with flexible-array members

Use flexible-array members in struct fc_fdmi_attr_entry and fs_fdmi_attrs
instead of one-element arrays, and refactor the code accordingly.

Also, this helps with the ongoing efforts to globally enable -Warray-bounds
and get us closer to being able to tighten the FORTIFY_SOURCE routines on
memcpy().

https://github.com/KSPP/linux/issues/79
https://github.com/ClangBuiltLinux/linux/issues/1590

Link: https://lore.kernel.org/r/20220214223903.GA859464@embeddedor
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>