ubsan: spu: left shift of negative value

ubsan: spu: left shift of negative value

Also fixes a real bug.  The DECODE_INSN_I9a and DECODE_INSN_I9b both
use UNSIGNED_EXTRACT for 7 low bits of the result, but this was an
unsigned value due to "insn" being unsigned.  DECODE_INSN_I9* is
therefore unsigned too, leading to a zero extension in an expression
using a bfd_vma if bfd_vma is 64 bits.

	* opcode/spu.h: Formatting.
	(UNSIGNED_EXTRACT): Use 1u.
	(SIGNED_EXTRACT): Don't sign extend with shifts.
	(DECODE_INSN_I9a, DECODE_INSN_I9b): Avoid left shift of signed value.
	Keep result signed.
	(DECODE_INSN_U9a, DECODE_INSN_U9b): Delete.