[SparcInstPrinter] Use the subtarget that is passed to the print function

instead of the one passed to the constructor.

Unfortunately, I don't have a test case for this change. In order to test my
change, I will have to run the code after line 90 in printSparcAliasInstr. I
couldn't make that happen because printAliasInstr would always handle the
printing of fcmp instructions that the code after line 90 is supposed to handle.

llvm-svn: 233471