test/crypto: fix minsize build

test/crypto: fix minsize build

Error occurs when configuring meson with --buildtype=minsize
with GCC 11.1.0:

app/test/test_cryptodev_blockcipher.c:1133:45: error:
‘blk_tcs’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
|         const struct blockcipher_test_case *blk_tcs;
|                                             ^~~~~~~

Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>