VAX: Use a mode iterator to produce individual interlocked branches

VAX: Use a mode iterator to produce individual interlocked branches

Regardless of the machine mode all the interlocked branches of the same
kind, one of the two provided by the ISA, use the same RTL patterns and
machine instructions, except for the memory operand's constraint.

Remove code duplication then and make use of a mode iterator combined
with an attribute to expand the same insn patterns with the constraint
suitably substituted from a single template.  No functional change.

	gcc/
	* config/vax/builtins.md (bb_mem): New mode attribute.
	(jbbssiqi, jbbssihi, jbbssisi): Fold insns into...
	(jbbssi<mode>): ... this.
	(jbbcciqi, jbbccihi, jbbccisi): Likewise...
	(jbbcci<mode>): ... this.