[Hexagon] Add a target feature to disable compound instructions

This affects the following instructions:
Tag: M4_mpyrr_addr     Syntax: Ry32 = add(Ru32,mpyi(Ry32,Rs32))
Tag: M4_mpyri_addr_u2  Syntax: Rd32 = add(Ru32,mpyi(#u6:2,Rs32))
Tag: M4_mpyri_addr     Syntax: Rd32 = add(Ru32,mpyi(Rs32,#u6))
Tag: M4_mpyri_addi     Syntax: Rd32 = add(#u6,mpyi(Rs32,#U6))
Tag: M4_mpyrr_addi     Syntax: Rd32 = add(#u6,mpyi(Rs32,Rt32))
Tag: S4_addaddi        Syntax: Rd32 = add(Rs32,add(Ru32,#s6))
Tag: S4_subaddi        Syntax: Rd32 = add(Rs32,sub(#s6,Ru32))
Tag: S4_or_andix       Syntax: Rx32 = or(Ru32,and(Rx32,#s10))
Tag: S4_andi_asl_ri    Syntax: Rx32 = and(#u8,asl(Rx32,#U5))
Tag: S4_ori_asl_ri     Syntax: Rx32 = or(#u8,asl(Rx32,#U5))
Tag: S4_addi_asl_ri    Syntax: Rx32 = add(#u8,asl(Rx32,#U5))
Tag: S4_subi_asl_ri    Syntax: Rx32 = sub(#u8,asl(Rx32,#U5))
Tag: S4_andi_lsr_ri    Syntax: Rx32 = and(#u8,lsr(Rx32,#U5))
Tag: S4_ori_lsr_ri     Syntax: Rx32 = or(#u8,lsr(Rx32,#U5))
Tag: S4_addi_lsr_ri    Syntax: Rx32 = add(#u8,lsr(Rx32,#U5))
Tag: S4_subi_lsr_ri    Syntax: Rx32 = sub(#u8,lsr(Rx32,#U5))