Revert "Xilinx mailbox and other updated in GNET device tree."

This reverts commit ed500d41dcfdfb84c63b8cb8a40bb216f8f24f42.
gsbd revert.
Meyer Sound SMPTE receiver support.
update-submodules
update-submodules
Merge remote branch 'origin/master'
update-submodules
submodules update.
Updated xilinx_lltemac PHY reset mechanism.
Re-enabled first attempt to initialize without reset.
gsbd submodule update.
gsbd submodule update.
gsbd submodule update.
gsbd submodule update.
gsbd submodule update.
update-submodules
update-submodules
update-submodules
Merge remote-tracking branch 'origin/master'
update-submodules