memory: emif: Add missing kerneldoc for lpmode

Add kerneldoc for 'lpmode' struct member to fix W=1 warnings:

  drivers/memory/emif.c:67 struct member 'lpmode' not described in 'emif_data'

Link: https://lore.kernel.org/r/20250525153435.15768-2-krzysztof.kozlowski@linaro.org
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

Author: krzk

drivers/memory/emif.c

@@ -39,6 +39,7 @@
  *				are two devices attached to this EMIF, this
  *				value is the maximum of the two temperature
  *				levels.
+ * @lpmode:			Chosen low power mode
  * @node:			node in the device list
  * @base:			base address of memory-mapped IO registers.
  * @dev:			device pointer.