arm64: tegra: Fix Tegra234 MGBE power-domains

The MGBE power-domains on Tegra234 are mapped to the MGBE controllers as
follows:

 MGBE0 (0x68000000) --> Power-Domain MGBEB
 MGBE1 (0x69000000) --> Power-Domain MGBEC
 MGBE2 (0x6a000000) --> Power-Domain MGBED

Update the device-tree nodes for Tegra234 to correct this.

Fixes: 610cdf31 ("arm64: tegra: Add MGBE nodes on Tegra234")
Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>