crypto: acomp - Fix CFI failure due to type punning

To avoid a crash when control flow integrity is enabled, make the
workspace ("stream") free function use a consistent type, and call it
through a function pointer that has that same type.

Fixes: 42d9f6c774 ("crypto: acomp - Move scomp stream allocation code into acomp")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Reviewed-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

include/crypto/internal/acompress.h

@@ -63,10 +63,7 @@ struct crypto_acomp_stream {
 struct crypto_acomp_streams {
 	/* These must come first because of struct scomp_alg. */
 	void *(*alloc_ctx)(void);
-	union {
-		void (*free_ctx)(void *);
-		void (*cfree_ctx)(const void *);
-	};
+	void (*free_ctx)(void *);
 
 	struct crypto_acomp_stream __percpu *streams;
 	struct work_struct stream_work;