backlight: lm3630a_bl: Remove invalid checks for unsigned int < 0

unsigned ints 'sources' and 'bank' cannot be less than LM3630A_SINK_0 (0)
and LM3630A_BANK_0 (0) respecitively, so change the logic to only check
for thier two possible valid values.

Fixes W=1 warnings:

drivers/video/backlight/lm3630a_bl.c: In function ‘lm3630a_parse_led_sources’:
drivers/video/backlight/lm3630a_bl.c:394:18: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits]
394 | if (sources[i] < LM3630A_SINK_0 || sources[i] > LM3630A_SINK_1)
| ^
drivers/video/backlight/lm3630a_bl.c: In function ‘lm3630a_parse_bank’:
drivers/video/backlight/lm3630a_bl.c:415:11: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits]
415 | if (bank < LM3630A_BANK_0 || bank > LM3630A_BANK_1)
| ^

Cc: Bartlomiej Zolnierkiewicz <[e-mail]>
Cc: Daniel Jeong <[e-mail]>
Cc: LDD MLP <[e-mail]>
Signed-off-by: Lee Jones <[e-mail]>
Reviewed-by: Daniel Thompson <[e-mail]>
Reviewed-by: Sam Ravnborg <[e-mail]>
Signed-off-by: Lee Jones <[e-mail]>

drivers/video/backlight/lm3630a_bl.c

···
 		return ret;
 
 	for (i = 0; i < num_sources; i++) {
-		if (sources[i] < LM3630A_SINK_0 || sources[i] > LM3630A_SINK_1)
+		if (sources[i] != LM3630A_SINK_0 && sources[i] != LM3630A_SINK_1)
 			return -EINVAL;
 
 		ret |= BIT(sources[i]);
···
 	if (ret)
 		return ret;
 
-	if (bank < LM3630A_BANK_0 || bank > LM3630A_BANK_1)
+	if (bank != LM3630A_BANK_0 && bank != LM3630A_BANK_1)
 		return -EINVAL;
 
 	led_sources = lm3630a_parse_led_sources(node, BIT(bank));