[SPARC] llvm-objdump seem to mishandle backwards branches

[koachan]

llvm-objdump seems to treat negative branch offset as a large positive one, causing it to disassemble backwards branch in an odd way:

reproducer:
  nop
  ba reproducer
   nop

Assemble with e.g. clang -target sparc -c reproducer.s, then read it back:

$ bin/llvm-objdump -d reproducer.o 

reproducer.o:	file format elf32-sparc

Disassembly of section .text:

00000000 <reproducer>:
       0: 01 00 00 00  	nop
       4: 10 bf ff ff  	ba 4194303
       8: 01 00 00 00  	nop

[llvmbot]

@llvm/issue-subscribers-tools-llvm-objdump

Author: Koakuma (koachan)

llvm-objdump seems to treat negative branch offset as a large positive one, causing it to disassemble backwards branch in an odd way: ``` reproducer: nop ba reproducer nop ```

Assemble with e.g. clang -target sparc -c reproducer.s, then read it back:

$ bin/llvm-objdump -d reproducer.o 

reproducer.o:	file format elf32-sparc

Disassembly of section .text:

00000000 <reproducer>:
       0: 01 00 00 00  	nop
       4: 10 bf ff ff  	ba 4194303
       8: 01 00 00 00  	nop

[MaskRay]

While updating the code, also port the InstPrinter change that has been done for popular ports (e.g. AArch64 https://reviews.llvm.org/D93241)