pds_core: ensure null-termination for firmware version strings

pds_core: ensure null-termination for firmware version strings

The driver passes fw_version directly to devlink_info_version_stored_put()
without ensuring null-termination. While current firmware null-terminates
these strings, the driver should not rely on this behavior. Add explicit
null-termination to prevent potential issues if firmware behavior changes.

Fixes: 45d76f492938 ("pds_core: set up device and adminq")
Signed-off-by: Nikhil P. Rao <nikhil.rao@amd.com>
Link: https://patch.msgid.link/20260520205842.1486718-1-nikhil.rao@amd.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>