cris: Emit trivial btstq expected by gcc.target/cris/sync-2i.c, sync-2c.c

cris: Emit trivial btstq expected by gcc.target/cris/sync-2i.c, sync-2c.c

As the added FIXME says, the new insn_and_split generates only a
small subset of the bit-tests that can be matched by "*btst" and
that were emitted by the undecc0rated cris.md at combine-time,
but it's naturally separable from a general variant by being
just what's needed for the test-cases that were previously
xfailed, and that no additional CCmodes are required.

gcc:
	PR target/93372
	* config/cris/cris.md (zcond): New code_iterator.
	("*cbranch<mode>4_btstq<CC>"): New insn_and_split.