x86/APX: optimize {nf} forms of ADD/SUB with specific immediates

x86/APX: optimize {nf} forms of ADD/SUB with specific immediates

Unlike for the legacy forms, where there's a difference in the resulting
EFLAGS, for the NF variants we can safely replace ones using 0x80 by the
respectively other insn while negating the immediate, saving 3 immediate
bytes (just 1 though for 16-bit operand size). Similarly we can replace
ones using 1 / -1 by INC/DEC (eliminating the immediate).