[SEM-503] UMBus Comm Issue

[alexborro]

Description

For some unknown / forgotten reason, the UMBus Drive Enable pin is connected to the serial (uart1) RTS pin, which makes no sense at all.
During update from kernel 4.14 to 5.15, the new UART driver began to drive this pin even when the serial is not open with hw flow control, blocking the UMbus communication.
The solution is a change in the device tree to remove the control of the pad USART3_RXD (wired to the UMBus Drive Enable signal) from the UART1 peripheral and connects it to the GPIO5 peripheral. That pad is now a gpio-hog pin of GPIO5 set to HIGH level.

How has this been tested

It was tested in an S6 and S8. The UMBus communication worked fine, including for firmware update.

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