crypto: arm64/sha256 - fix build when CONFIG_PREEMPT_VOLUNTARY=y

Fix the build of sha256-ce.S when CONFIG_PREEMPT_VOLUNTARY=y by passing
the correct label to the cond_yield macro.  Also adjust the code to
execute only one branch instruction when CONFIG_PREEMPT_VOLUNTARY=n.

Fixes: 6e36be51 ("crypto: arm64/sha256 - implement library instead of shash")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202505071811.yYpLUbav-lkp@intel.com/


Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>