solaris: implement blockdev size getting

Just use lseek(..., SEEK_END), we should actually be able to use that
on all platforms.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/os/os-solaris.h b/os/os-solaris.h
index f00aae1..c49ce8d 100644
--- a/os/os-solaris.h
+++ b/os/os-solaris.h
@@ -28,7 +28,13 @@
  */
 static inline int blockdev_size(int fd, unsigned long long *bytes)
 {
-	return EINVAL;
+	off_t end = lseek(fd, 0, SEEK_END);
+
+	if (end < 0)
+		return errno;
+
+	*bytes = end;
+	return 0;
 }
 
 static inline int blockdev_invalidate_cache(int fd)