orangefs: add usercopy whitelist to orangefs_op_cache

orangefs: add usercopy whitelist to orangefs_op_cache

orangefs_op_cache is created with kmem_cache_create(), which provides
no usercopy whitelist. orangefs_devreq_read() copies the tag and upcall
fields directly from slab objects to userspace via copy_to_user(). With
CONFIG_HARDENED_USERCOPY enabled, this triggers usercopy_abort().

Switch to kmem_cache_create_usercopy() with a whitelist covering the
tag and upcall fields, matching the pattern already used by
orangefs_inode_cache in super.c.

Signed-off-by: Ziyi Guo <n7l8m4@u.northwestern.edu>
Signed-off-by: Mike Marshall <hubcap@omnibond.com>