Rename crc functions to private namespace

Apparently we overlap with some gtk (?) crc32() functions, causing
ours to be called and subsequently crashing since the arguments
aren't the same.

Move everything to a fio_ protected namespace.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/crc/sha256.c b/crc/sha256.c
index dcb1677..3a72a5b 100644
--- a/crc/sha256.c
+++ b/crc/sha256.c
@@ -227,7 +227,7 @@
 	memset(W, 0, 64 * sizeof(uint32_t));
 }
 
-void sha256_init(struct sha256_ctx *sctx)
+void fio_sha256_init(struct fio_sha256_ctx *sctx)
 {
 	sctx->state[0] = H0;
 	sctx->state[1] = H1;
@@ -240,8 +240,8 @@
 	sctx->count[0] = sctx->count[1] = 0;
 }
 
-void sha256_update(struct sha256_ctx *sctx, const uint8_t *data,
-		   unsigned int len)
+void fio_sha256_update(struct fio_sha256_ctx *sctx, const uint8_t *data,
+		       unsigned int len)
 {
 	unsigned int i, idx, part_len;