[committed] Provide suitable output template for zero_extendqihi2 on H8

[committed] Provide suitable output template for zero_extendqihi2 on H8

Segher's recent combine change, quite unexpectedly, triggered a regression on
the H8 port.  It failed to build newlib.

The zero_extendqihi2 pattern provided two alternatives.  One where the source
and destination matched.  That turns into a suitable instruction trivially.
The second alternative was actually meant to capture cases where the value is
coming from memory.

What was missing here was the reg->reg case where the source and destination do
not match.  That fell into the second case which was requested to be split by
the pattern's output template.

The splitter had a suitable condition to make sure it only triggered in the
right cases.  Unfortunately with the pattern requiring a split in a case where
the splitter was going to fail led to the fault.

So regardless of what's going on in the combiner, this code was just wrong.
Fixed thusly by providing a suitable output template for the reg->reg case.

Regression tested on h8300-elf.  Pushing to the trunk.

gcc/

	* config/h8300/extensions.md (zero_extendqihi*): Add output
	template for reg->reg case where the regs don't match.