platform/x86: int3472: Use local variable for LED struct access

platform/x86: int3472: Use local variable for LED struct access

Introduce a local struct int3472_pled pointer in the LED registration,
unregistration, and brightness callback functions to avoid repeatedly
dereferencing int3472->pled. In the brightness callback, use
container_of() to get the int3472_pled struct directly instead of
going through int3472_discrete_device.

No functional change.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Hans de Goede <johannes.goede@oss.qualcomm.com>
Signed-off-by: Marco Nenciarini <mnencia@kcore.it>
Link: https://patch.msgid.link/20260401203638.1601661-2-mnencia@kcore.it
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>