drivers: interrupt_controller: change dt macro

Replace the use of `DT_NODELABEL(exti)` which depends on the node label
with the defined EXTI_NODE macro using the instance with the
`st_stm32_exti` compatible.
Since both macros point to the same node, this change doesn't affect
the code logic, but makes it independent of the node label, in
preparation for the addition of the STM32MP2 exti nodes.

Signed-off-by: Youssef Zini <youssef.zini@savoirfairelinux.com>

Author: youssefz24

drivers/interrupt_controller/intc_exti_stm32.c

@@ -35,7 +35,7 @@ struct stm32_exti_range {
 	uint8_t len;
 };
 
-#define NUM_EXTI_LINES DT_PROP(DT_NODELABEL(exti), num_lines)
+#define NUM_EXTI_LINES DT_PROP(EXTI_NODE, num_lines)
 
 static IRQn_Type exti_irq_table[NUM_EXTI_LINES] = {[0 ... NUM_EXTI_LINES - 1] = 0xFF};
 
@@ -220,7 +220,7 @@ static int stm32_exti_init(const struct device *dev)
 {
 	ARG_UNUSED(dev);
 
-	DT_FOREACH_PROP_ELEM(DT_NODELABEL(exti),
+	DT_FOREACH_PROP_ELEM(EXTI_NODE,
 			     interrupt_names,
 			     STM32_EXTI_INIT_LINE_RANGE);