[nrf fromlist] tests: kernel: interrupt: Fix for nRF54H20 FLPR

Use designated IRQ numbers, instead of generic defaults.

Upstream PR #: 91910
Signed-off-by: Grzegorz Swiderski <grzegorz.swiderski@nordicsemi.no>

Author: 57300

tests/kernel/interrupt/src/nested_irq.c

@@ -56,7 +56,8 @@
  */
 #define IRQ0_PRIO	IRQ_DEFAULT_PRIORITY
 #define IRQ1_PRIO	0x0
-#elif defined(CONFIG_SOC_SERIES_NRF54LX) && defined(CONFIG_RISCV_CORE_NORDIC_VPR)
+#elif (defined(CONFIG_SOC_SERIES_NRF54LX) || defined(CONFIG_SOC_NRF54H20_CPUFLPR)) && \
+	defined(CONFIG_RISCV_CORE_NORDIC_VPR)
 #define IRQ0_LINE	16
 #define IRQ1_LINE	17