drivers/flash/qspi_nor_flash: Remove dev null check

The commit removes dev != NULL check from qspi_nrfx_configure.

Signed-off-by: Dominik Ermel <dominik.ermel@nordicsemi.no>
diff --git a/drivers/flash/nrf_qspi_nor.c b/drivers/flash/nrf_qspi_nor.c
index 3875d84..52b3aab 100644
--- a/drivers/flash/nrf_qspi_nor.c
+++ b/drivers/flash/nrf_qspi_nor.c
@@ -650,10 +650,6 @@
 /* Configures QSPI memory for the transfer */
 static int qspi_nrfx_configure(const struct device *dev)
 {
-	if (!dev) {
-		return -ENXIO;
-	}
-
 	struct qspi_nor_data *dev_data = dev->data;
 
 	qspi_fill_init_struct(&QSPIconfig);