BugLink: https://bugs.launchpad.net/bugs/1858489

[ Upstream commit 0fbc9b8b ]

This fixes a compilation warning in sysfs.c

drivers/infiniband/hw/mlx4/sysfs.c:360:2: warning: 'strncpy' output may be
truncated copying 8 bytes from a string of length 31
[-Wstringop-truncation]

By eliminating the temporary stack buffer.
Signed-off-by: Qian Cai <cai@gmx.us>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>