target-ppc: Add DFP to Emulated Instructions Flag

Decimal Floating Point is emulated, so add it the mask.  This will
fix the erroneous message:

  Warning: Disabling some instructions which are not emulated by TCG (0x0, 0x4)

Signed-off-by: Tom Musta <tommusta@gmail.com>
Signed-off-by: Alexander Graf <agraf@suse.de>