samples: i2s: output: add nucleo_wba55cg

Add nucleo_wba55cg in samples/drivers/i2s/output

Signed-off-by: Mario Paja <mariopaja@hotmail.com>

Author: mariopaja

samples/drivers/i2s/output/boards/nucleo_wba55cg.conf

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+CONFIG_HEAP_MEM_POOL_SIZE=4192

samples/drivers/i2s/output/boards/nucleo_wba55cg.overlay

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+/*
+ * Copyright (c) 2025 Mario Paja
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/ {
+	aliases {
+		i2s-tx = &sai1_b;
+	};
+};
+
+&pll1 {
+	/* 43.526KHz (-1.3% Error) */
+	div-m = <4>;
+	mul-n = <19>;
+	div-r = <2>;
+	div-q = <2>;
+	div-p = <14>;
+	clocks = <&clk_hse>;
+	status = "okay";
+};
+
+&gpdma1 {
+	status = "okay";
+};
+
+&sai1_b {
+	pinctrl-0 = <&sai1_mclk_b_pb4 &sai1_sd_b_pb7 &sai1_fs_b_pb5 &sai1_sck_b_pb6>;
+	pinctrl-names = "default";
+	status = "okay";
+	mclk-enable;
+	mclk-divider = "div-256";
+	dma-names = "tx";
+};
+
+/* conflicts with SAI */
+&spi1 {
+	status = "disabled";
+};
+
+/* conflicts with SAI */
+&lpuart1 {
+	status = "disabled";
+};