leds: spi-byte: Utilise temporary variable for struct device

We have a temporary variable to keep a pointer to struct device.
Utilise it where it makes sense.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20240606173037.3091598-5-andriy.shevchenko@linux.intel.com


Signed-off-by: Lee Jones <lee@kernel.org>