powerpc/sstep: Add support for divde[.] and divdeu[.] instructions

This patch adds emulation support for divde, divdeu instructions,
  - Divide Doubleword Extended (divde[.])
  - Divide Doubleword Extended Unsigned (divdeu[.])

Signed-off-by: Balamuruhan S <bala24@linux.ibm.com>
Reviewed-by: Sandipan Das <sandipan@linux.ibm.com>
Acked-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200728130308.1790982-3-bala24@linux.ibm.com