Made sure the constructor for insts use ExtMachInst rather than MachInst, since other...

Made sure the constructor for insts use ExtMachInst rather than MachInst, since otherwise the EXT_ASI field is lost.

src/arch/sparc/isa/base.isa:
src/arch/sparc/isa/formats/micro.isa:
    Switch MachInst to ExtMachInst so that the EXT_ASI field is available to the instructions.
src/arch/sparc/utility.hh:
    Made sure EXT_ASI was set to the appropriate ASI value whether or not the asi register was used.

--HG--
extra : convert_revision : cc4363dfe7da81969959cec9d5ad48528edeb8ce