irqchip/renesas-rzg2l: Simplify checks in rzg2l_irqc_common_init()

Both devm_pm_runtime_enable() and pm_runtime_resume_and_get()
return 0 or a negative error code.

Simplify the checks done with their respective return values
accordingly.

Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@renesas.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250212182034.366167-7-fabrizio.castro.jz@renesas.com