rs6000: Add second variant of adde

rs6000: Add second variant of adde

This adds a second variant of the adde insn pattern, this one with the
CA register as the second operand.  The existing pattern has it as the
third operand.  It would be ideal if RTL was always canonicalised like
that, but it isn't (and that is not trivial), and this is a simple and
harmless patch.

	* config/rs6000/rs6000.md (*add<mode>3_carry_in_internal2): New.

From-SVN: r255259