firmware: coreboot: framebuffer: Avoid invalid zero physical address

On ARM64 systems coreboot defers framebuffer allocation to its payload,
to be done by a libpayload function call. In this case, coreboot tables
still include a framebuffer entry with display format details, but the
physical address field is set to zero (as in [1], for example).

Unfortunately, this field is not automatically updated when the
framebuffer is initialized through libpayload, citing that doing so
would invalidate checksums over the entire coreboot table [2].

This can be observed on ARM64 Chromebooks with stock firmware. On a
Google Kevin (RK3399), trying to use coreboot framebuffer driver as
built-in to the kernel results in a benign error. But on Google Hana
(MT8173) and Google Cozmo (MT8183) it causes a hang.

When the framebuffer physical address field in the coreboot table is
zero, we have no idea where coreboot initialized a framebuffer, or even
if it did. Instead of trying to set up a framebuffer located at zero,
return ENODEV to indicate that there isn't one.

[1] https://review.coreboot.org/c/coreboot/+/17109
[2] https://review.coreboot.org/c/coreboot/+/8797

Signed-off-by: Alper Nebi Yasak <[email protected]>
Reviewed-by: Julius Werner <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Tzung-Bi Shih <[email protected]>

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