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 <[e-mail]>
Signed-off-by: Herbert Xu <[e-mail]>

lib/crypto/arc4.c

···
 }
 EXPORT_SYMBOL(arc4_crypt);
 
+MODULE_DESCRIPTION("ARC4 Cipher Algorithm");
 MODULE_LICENSE("GPL");

lib/crypto/des.c

···
 }
 EXPORT_SYMBOL_GPL(des3_ede_decrypt);
 
+MODULE_DESCRIPTION("DES & Triple DES EDE Cipher Algorithms");
 MODULE_LICENSE("GPL");

lib/crypto/libchacha.c

···
 }
 EXPORT_SYMBOL(chacha_crypt_generic);
 
+MODULE_DESCRIPTION("ChaCha stream cipher (RFC7539)");
 MODULE_LICENSE("GPL");

lib/crypto/poly1305.c

···
 
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Martin Willi <[e-mail]>");
+MODULE_DESCRIPTION("Poly1305 authenticator algorithm, RFC7539");