arch-power: Add fixed-point doubleword rotate instructions

arch-power: Add fixed-point doubleword rotate instructions

This adds the following rotate instructions:
  * Rotate Left Doubleword Immediate then Clear Left (rldicl[.])
  * Rotate Left Doubleword Immediate then Clear Right (rldicr[.])
  * Rotate Left Doubleword Immediate then Clear (rldic[.])
  * Rotate Left Doubleword then Clear Left (rldcl[.])
  * Rotate Left Doubleword then Clear Right (rldcr[.])
  * Rotate Left Doubleword Immediate then Mask Insert (rldimi[.])

Change-Id: I27520314e738e5bed92bf07c1150943c9f83e881
Signed-off-by: Sandipan Das <sandipan@linux.vnet.ibm.com>