crypto: xor - Fix warning when XOR_SELECT_TEMPLATE is unset

This patch fixes an unused label warning triggered when the macro
XOR_SELECT_TEMPLATE is not set.

Fixes: 39457acd ("crypto: xor - skip speed test if the xor...")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Suggested-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>