Faults: Turn off arch/faults.hh

Because there are no longer architecture independent but specialized functions
in arch/XXX/faults.hh, code that isn't using the faults from a particular ISA
no longer needs to be able to include them through the switching header file
arch/faults.hh. By removing that header file (arch/faults.hh), the potential
interface between ISA code and non ISA code is narrowed.

src/arch/SConscript

@@ -43,7 +43,6 @@ Import('*')
 
 # List of headers to generate
 isa_switch_hdrs = Split('''
-        faults.hh
         interrupts.hh
         isa.hh
         isa_traits.hh