fix: Fix Boot for EVR PCie
Split the boot snippets, one for MTCA and other for PCIe. They are loaded based on the macro EVRMODEL (Mtca or Pcie). This way the backplane configuration is set only for MTCA ones. The default model is MTCA.
The PCIe boot snippet is almost empty but it can have specific configuration on the future.
Edited by Gabriel Fedel