spi: stm32-qspi: manage the get_irq error case

During probe, check the "get_irq" error value.

Signed-off-by: Fabien Dessenne <fabien.dessenne@st.com>
Acked-by: Ludovic Barre <ludovic.barre@st.com>
Signed-off-by: Mark Brown <broonie@kernel.org>