net/mlx5: improve some comments

[ Upstream commit 6533380d ]

Replaced "its" with "it's".

Signed-off-by: Hu Haowen <xianfengting221@163.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Stable-dep-of: 4261edf1 ("net/mlx5: Fix fw tracer first block check")
Signed-off-by: Sasha Levin <sashal@kernel.org>