tests: drivers: spi: spi_loopback: update gpdma1 request sel

According to wba55 refman RM0493, gpdma1 request for
spi1_rx_dma and spi1_tx_dma is 1 and 2.

solve failed test on drivers.spi.stm32_spi_dma.loopback
scenario.

Signed-off-by: Fabrice DJIATSA <[email protected]>

Author: djiatsaf-st

tests/drivers/spi/spi_loopback/boards/nucleo_wba55cg.overlay

@@ -9,8 +9,8 @@
 };
 
 &spi1 {
-	dmas = <&gpdma1 0 7 STM32_DMA_PERIPH_TX
-		&gpdma1 1 6 STM32_DMA_PERIPH_RX>;
+	dmas = <&gpdma1 0 2 STM32_DMA_PERIPH_TX
+		&gpdma1 1 1 STM32_DMA_PERIPH_RX>;
 	dma-names = "tx", "rx";
 	slow@0 {
 		compatible = "test-spi-loopback-slow";