spi_nxp_lpspi: Fix DMA Async API

Fix the ASYNC DMA API on the lpspi driver and actually make the entire
driver go through that path. Rather than having an orthogonal
internally synchronous path we can just have both APIs go through the
same asynchronous path and just use wait_for_completion from spi context
to implement either sync or async.

Also make DMA driver default y if dependency (an lpspi having dmas
property) is met.

And lpspi_wait_tx_fifo_empty can be shared between drivers.

Signed-off-by: Declan Snyder <declan.snyder@nxp.com>

Author: decsny

drivers/spi/spi_nxp_lpspi/Kconfig

@@ -14,6 +14,7 @@ if SPI_MCUX_LPSPI
 
 config SPI_MCUX_LPSPI_DMA
 	bool "MCUX LPSPI SPI DMA Support"
+	default y
 	select DMA
 	depends on $(dt_compat_any_has_prop,$(DT_COMPAT_NXP_LPSPI),dmas)
 	help

drivers/spi/spi_nxp_lpspi/spi_nxp_lpspi.c

@@ -16,14 +16,6 @@ struct lpspi_driver_data {
 	uint8_t word_size_bytes;
 };
 
-static inline void lpspi_wait_tx_fifo_empty(const struct device *dev)
-{
-	LPSPI_Type *base = (LPSPI_Type *)DEVICE_MMIO_NAMED_GET(dev, reg_base);
-
-	while (LPSPI_GetTxFifoCount(base) != 0) {
-	}
-}
-
 static inline uint8_t rx_fifo_cur_len(LPSPI_Type *base)
 {
 	return (base->FSR & LPSPI_FSR_RXCOUNT_MASK) >> LPSPI_FSR_RXCOUNT_SHIFT;

drivers/spi/spi_nxp_lpspi/spi_nxp_lpspi_common.c

@@ -9,6 +9,14 @@ LOG_MODULE_REGISTER(spi_mcux_lpspi_common, CONFIG_SPI_LOG_LEVEL);
 
 #include "spi_nxp_lpspi_priv.h"
 
+void lpspi_wait_tx_fifo_empty(const struct device *dev)
+{
+	LPSPI_Type *base = (LPSPI_Type *)DEVICE_MMIO_NAMED_GET(dev, reg_base);
+
+	while (LPSPI_GetTxFifoCount(base) != 0) {
+	}
+}
+
 int spi_mcux_release(const struct device *dev, const struct spi_config *spi_cfg)
 {
 	struct spi_mcux_data *data = dev->data;