image: Use the correct checks for CRC32

Add a host Kconfig for CRC32. With this we can use CONFIG_IS_ENABLED(CRC32)
directly in the host build, so drop the unnecessary indirection.

Add a few more conditions to SPL_CRC32 to avoid build failures as well as
TPL_CRC32. Also update hash.c to make crc32 optional and to actually take
notice of SPL_CRC32.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
diff --git a/common/hash.c b/common/hash.c
index 3b591ba0..79202e1 100644
--- a/common/hash.c
+++ b/common/hash.c
@@ -178,7 +178,7 @@
 	return 0;
 }
 
-static int hash_init_crc32(struct hash_algo *algo, void **ctxp)
+static int __maybe_unused hash_init_crc32(struct hash_algo *algo, void **ctxp)
 {
 	uint32_t *ctx = malloc(sizeof(uint32_t));
 	*ctx = 0;
@@ -186,15 +186,16 @@
 	return 0;
 }
 
-static int hash_update_crc32(struct hash_algo *algo, void *ctx,
-			     const void *buf, unsigned int size, int is_last)
+static int __maybe_unused hash_update_crc32(struct hash_algo *algo, void *ctx,
+					    const void *buf, unsigned int size,
+					    int is_last)
 {
 	*((uint32_t *)ctx) = crc32(*((uint32_t *)ctx), buf, size);
 	return 0;
 }
 
-static int hash_finish_crc32(struct hash_algo *algo, void *ctx, void *dest_buf,
-			     int size)
+static int __maybe_unused hash_finish_crc32(struct hash_algo *algo, void *ctx,
+					    void *dest_buf, int size)
 {
 	if (size < algo->digest_size)
 		return -1;
@@ -311,6 +312,7 @@
 		.hash_update	= hash_update_crc16_ccitt,
 		.hash_finish	= hash_finish_crc16_ccitt,
 	},
+#if CONFIG_IS_ENABLED(CRC32)
 	{
 		.name		= "crc32",
 		.digest_size	= 4,
@@ -320,6 +322,7 @@
 		.hash_update	= hash_update_crc32,
 		.hash_finish	= hash_finish_crc32,
 	},
+#endif
 };
 
 /* Try to minimize code size for boards that don't want much hashing */