feat(arm_fpga): write UART baud base clock frequency into DTB

Since we now autodetect the actual system frequency, which is also used
as the base for the UART baudrate generation, we should update the value
currently hard-coded in the DT. Otherwise Linux will reprogram the
divider using a potentially wrong base rate, which breaks the UART

Find the DT node referenced by the UART node as the clock rate, and set
the "clock-frequency" property in that node to the detected system
frequency. This will let Linux reprogram the divider to the same value,
preserving the actual baudrate.

Change-Id: Ib5a936849f2198577b86509f032751d5386ed2f8
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
1 file changed