arm64: dts: apple: t8103: Remove PCIe max-link-speed properties

The driver doesn't support these, they shouldn't be in the SoC include
anyway, and we're now configuring this in the bootloader instead. This
also solves the j274 1G/10G Ethernet variant discrepancy, since that
will now be configured properly based on the dynamic ADT property.

Acked-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Hector Martin <marcan@marcan.st>