target/ppc: support for 32-bit carry and overflow

POWER ISA 3.0 adds CA32 and OV32 status in 64-bit mode. Add the flags
and corresponding defines.

Moreover, CA32 is updated when CA is updated and OV32 is updated when OV
is updated.

Arithmetic instructions:
    * Addition and Substractions:

        addic, addic., subfic, addc, subfc, adde, subfe, addme, subfme,
        addze, and subfze always updates CA and CA32.

        => CA reflects the carry out of bit 0 in 64-bit mode and out of
           bit 32 in 32-bit mode.
        => CA32 reflects the carry out of bit 32 independent of the
           mode.

        => SO and OV reflects overflow of the 64-bit result in 64-bit
           mode and overflow of the low-order 32-bit result in 32-bit
           mode
        => OV32 reflects overflow of the low-order 32-bit independent of
           the mode

    * Multiply Low and Divide:

        For mulld, divd, divde, divdu and divdeu: SO, OV, and OV32 bits
        reflects overflow of the 64-bit result

        For mullw, divw, divwe, divwu and divweu: SO, OV, and OV32 bits
        reflects overflow of the 32-bit result

     * Negate with OE=1 (nego)

       For 64-bit mode if the register RA contains
       0x8000_0000_0000_0000, OV and OV32 are set to 1.

       For 32-bit mode if the register RA contains 0x8000_0000, OV and
       OV32 are set to 1.

Signed-off-by: Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
