U-Boot was hanging on hardware, but not Qemu. This is because on
the machines tested, namely the X200 and E6230 laptops supported
in Libreboot, the UART was disabled from coreboot.
This U-Boot patch from Simon Glass works around the issue by
silently disabling the UART when it isn't there. Instead,
output is sent to the display and U-Boot no longer hangs.
Signed-off-by: Leah Rowe <leah@libreboot.org>
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