crypto: lib - add missing MODULE_DESCRIPTION() macros

Fix the allmodconfig 'make W=1' warnings:
WARNING: modpost: missing MODULE_DESCRIPTION() in lib/crypto/libchacha.o
WARNING: modpost: missing MODULE_DESCRIPTION() in lib/crypto/libarc4.o
WARNING: modpost: missing MODULE_DESCRIPTION() in lib/crypto/libdes.o
WARNING: modpost: missing MODULE_DESCRIPTION() in lib/crypto/libpoly1305.o

Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>