Fixed ordering of elements in instructions: although the binary instructions

list (rd, rs1, imm), in that order (bit-wise), the actual assembly syntax is
instr rd, imm, rs1, and that is how they are constructed in the instruction
selector. This fixes the discrepancy.

Also fixed some comments along the same lines and fixed page numbers referring
to where instructions are described in the Sparc manual.

llvm-svn: 6384