wifi: ray_cs: Utilize strnlen() in parse_addr()

[ Upstream commit 9e8e9187673cb24324f9165dd47b2b28f60b0b10 ]

Instead of doing simple operations and using an additional variable on stack,
utilize strnlen() and reuse len variable.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220603164414.48436-1-andriy.shevchenko@linux.intel.com


Stable-dep-of: 4f8d66a9fb2e ("wifi: ray_cs: Fix an error handling path in ray_probe()")
Signed-off-by: Sasha Levin <sashal@kernel.org>