mimxrt/machine_uart: Use a wrapper function to handle IRQ idle support.

MicroPython needs to handle the UART idle interrupt, which is not something
that the standard SDK provides.  This was previously fixed by including in
the mimxrt port a modified copy of `fsl_lpuart.c`.

This commit changes how that's done by building the unmodified
`fsl_lpuart.c` directly from the SDK, and using linker wrapping to override
the necessary functions to get at the idle IRQ.  As part of this, the code
is updated to work with the latest SDK.

Signed-off-by: Andrew Leech <andrew.leech@planetinnovation.com.au>

Author: pi-anl

ports/mimxrt/Makefile

@@ -137,6 +137,7 @@ SRC_HAL_IMX_C += \
 	$(MCUX_SDK_DIR)/drivers/lpi2c/fsl_lpi2c.c \
 	$(MCUX_SDK_DIR)/drivers/lpspi/fsl_lpspi.c \
 	$(MCUX_SDK_DIR)/drivers/lpspi/fsl_lpspi_edma.c \
+	$(MCUX_SDK_DIR)/drivers/lpuart/fsl_lpuart.c \
 	$(MCUX_SDK_DIR)/drivers/pit/fsl_pit.c \
 	$(MCUX_SDK_DIR)/drivers/pwm/fsl_pwm.c \
 	$(MCUX_SDK_DIR)/drivers/sai/fsl_sai.c \
@@ -152,6 +153,10 @@ else
 SRC_HAL_IMX_C += $(MCU_DIR)/xip/fsl_flexspi_nor_boot.c
 endif
 
+# UART IRQ wrapper for UART.IRQ_RXIDLE support (see machine_uart.c for implementation details)
+# Double wrapping is required because SDK stores function pointers in s_lpuartIsr[] dispatch table
+LDFLAGS += --wrap=LPUART_TransferCreateHandle --wrap=LPUART_TransferHandleIRQ
+
 INC_HAL_IMX += \
 	-I$(TOP)/$(MCU_DIR) \
 	-I$(TOP)/$(MCU_DIR)/drivers \
@@ -244,7 +249,6 @@ SRC_C += \
 	eth.c \
 	fatfs_port.c \
 	flash.c \
-	hal/fsl_lpuart.c \
 	hal/pwm_backport.c \
 	help.c \
 	led.c \
@@ -505,7 +509,8 @@ LDFLAGS += \
 	--cref \
 	--gc-sections \
 	--print-memory-usage \
-	-Map=$@.map
+	-Map=$@.map \
+    --wrap=LPUART_TransferCreateHandle --wrap=LPUART_TransferHandleIRQ
 
 # LDDEFINES are used for link time adaptation of linker scripts, utilizing
 #	the C preprocessor. Therefore keep LDDEFINES separated from LDFLAGS!