hwmon: (pwm-fan) Add const to channels allocation type

In preparation for making the devm_kmalloc family of allocators type
aware, we need to make sure that the returned type from the allocation
matches the type of the variable being assigned. (Before, the allocator
would always return "void *", which can be implicitly cast to any
pointer type.)

The assigned type is "const struct hwmon_channel_info **", but the
converted allocation type would be "struct hwmon_channel_info **", which
is the same type without the const qualifier. As there is no general way
to safely add const qualifiers, take the size from the assignment target
instead. No change in allocation size results.

Build tested ARCH=x86_64 allmodconfig with GCC 16.2.0:
drivers/hwmon/pwm-fan.o

Assisted-by: LLM coccinelle
Signed-off-by: Kees Cook <kees+treewide@kernel.org>
Link: https://patch.msgid.link/20260917211417.i.173-kees@kernel.org
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/pwm-fan.c

@@ -619,7 +619,7 @@ static int pwm_fan_probe(struct platform_device *pdev)
 	}
 
 	channels = devm_kcalloc(dev, channel_count + 1,
-				sizeof(struct hwmon_channel_info *), GFP_KERNEL);
+				sizeof(*channels), GFP_KERNEL);
 	if (!channels)
 		return -ENOMEM;