ubsan: nds32: left shift cannot be represented in type 'int'

ubsan: nds32: left shift cannot be represented in type 'int'

Note that using 1u in N32_BIT makes all of N32_BIT, __MASK, __MF, __GF
and __SEXT evaluate as unsigned int (the latter three when when their
v arg is int or smaller).  This would be a problem if assigning the
result to a bfd_vma, long, or other type wider than an int since the
__SEXT result would be zero extended to the wider type.  Fortunately
nds32 target code doesn't use wider types unnecessarily.

include/
	* opcode/nds32.h (N32_BIT): Define using 1u.
	(__SEXT): Use __MASK and N32_BIT.
	(N32_IMMS): Remove duplicate mask.
opcodes/
	* nds32-dis.c (print_insn16, print_insn32): Remove forward decls.
	(struct objdump_disasm_info): Delete.
	(nds32_parse_audio_ext, nds32_parse_opcode): Cast result of
	N32_IMMS to unsigned before shifting left.