dev, mips: Remove the unused MaltaPChip class

The MaltaPChip class is currently unused and identical (except for the
class name) to the TsunamiPChip. If someone decides to implement PCI
for Malta, they should make sure to share code with the Tsunami
implementation if they are similar.

src/dev/mips/SConscript

@@ -39,4 +39,4 @@ if env['TARGET_ISA'] == 'mips':
     Source('malta.cc')
     Source('malta_cchip.cc')
     Source('malta_io.cc')
-    Source('malta_pchip.cc')
+