powerpc/ppc-opcode: Reuse raw instruction macros to stringify

Wrap existing stringify macros to reuse raw instruction encoding
macros that are newly added.

Signed-off-by: Balamuruhan S <bala24@linux.ibm.com>
Tested-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Acked-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
[mpe: Add DCBFPS, DCBSTPS, PHWSYNC, PLWSYNC]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200624113038.908074-6-bala24@linux.ibm.com