Set both MBUS/PBUS in configs | Add simple check for correct clocks

generators/chipyard/src/main/scala/config/AbstractConfig.scala

@@ -45,6 +45,7 @@ class AbstractConfig extends Config(
   new chipyard.config.WithNoSubsystemDrivenClocks ++             // drive the subsystem diplomatic clocks from ChipTop instead of using implicit clocks
   new chipyard.config.WithInheritBusFrequencyAssignments ++      // Unspecified clocks within a bus will receive the bus frequency if set
   new chipyard.config.WithPeripheryBusFrequencyAsDefault ++      // Unspecified frequencies with match the pbus frequency (which is always set)
+  new chipyard.config.WithMemoryBusFrequency(100.0) ++           // Default 100 MHz mbus
   new chipyard.config.WithPeripheryBusFrequency(100.0) ++        // Default 100 MHz pbus
   new freechips.rocketchip.subsystem.WithJtagDTM ++              // set the debug module to expose a JTAG port
   new freechips.rocketchip.subsystem.WithNoMMIOPort ++           // no top-level MMIO master port (overrides default set in rocketchip)