Complete the basic integer instruction set and add related predictor in CSKY.td.
And it includes the instruction definition and asm parser support.
Differential Revision: https://reviews.llvm.org/D111701
This basic parser will handle basic instructions with register or immediate operands.
With the addition of CSKYInstPrinter, we can now make use of lit tests.
Differential Revision: https://reviews.llvm.org/D93798