[nios2] Add missing Nios2CodeGen -> Nios2AsmPrinter linkage

[mgorny]

Summary

Add missing linkage from Nios2CodeGen library to Nios2AsmPrinter
library. The missing dependency causes shared-lib build to fail with
the following reason:

lib/Target/Nios2/CMakeFiles/LLVMNios2CodeGen.dir/Nios2AsmPrinter.cpp.o: In function `(anonymous namespace)::Nios2AsmPrinter::PrintAsmMemoryOperand(llvm::MachineInstr const*, unsigned int, unsigned int, char const*, llvm::raw_ostream&)':
Nios2AsmPrinter.cpp:(.text._ZN12_GLOBAL__N_115Nios2AsmPrinter21PrintAsmMemoryOperandEPKN4llvm12MachineInstrEjjPKcRNS1_11raw_ostreamE+0x2b): undefined reference to `llvm::Nios2InstPrinter::getRegisterName(unsigned int)'
lib/Target/Nios2/CMakeFiles/LLVMNios2CodeGen.dir/Nios2AsmPrinter.cpp.o: In function `(anonymous namespace)::Nios2AsmPrinter::PrintAsmOperand(llvm::MachineInstr const*, unsigned int, unsigned int, char const*, llvm::raw_ostream&)':
Nios2AsmPrinter.cpp:(.text._ZN12_GLOBAL__N_115Nios2AsmPrinter15PrintAsmOperandEPKN4llvm12MachineInstrEjjPKcRNS1_11raw_ostreamE+0x97): undefined reference to `llvm::Nios2InstPrinter::getRegisterName(unsigned int)'
collect2: error: ld returned 1 exit status

[mgorny]

Gentle ping.

[mgorny]

Ping.

[mgorny]

Piiing.

[chapuni]

I think such a fixup may be "obvious". Go ahead!

llvm/trunk/lib/Target/Nios2/LLVMBuild.txt

 #dependencies for this component.When tools are built, the build system will
 #include the transitive closure of all required_libraries for the components
 #the tool needs.
 required_libraries = AsmPrinter
                      CodeGen
                      Core
                      GlobalISel
                      MC
+                     Nios2AsmPrinter
                      Nios2Desc
                      Nios2Info
                      SelectionDAG
                      Support
                      Target
 #end of required_libraries
 
 #All LLVMBuild.txt in Target / Nios2 and subdirectory use 'add_to_library_groups
 #= Nios2'
 add_to_library_groups = Nios2