leds: qcom-lpg: Annotate struct lpg_led with __counted_by

Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
(for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

As found with Coccinelle[1], add __counted_by for struct lpg_led.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocciSigned-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20230915201059.never.086-kees@kernel.orgSigned-off-by: Lee Jones <lee@kernel.org>

drivers/leds/rgb/leds-qcom-lpg.c

@@ -173,7 +173,7 @@ struct lpg_led {
 	struct led_classdev_mc mcdev;
 
 	unsigned int num_channels;
-	struct lpg_channel *channels[];
+	struct lpg_channel *channels[] __counted_by(num_channels);
 };
 
 /**