py/stream: Move definition of mp_stream_p_t from obj.h to stream.h.

Since a long time now, mp_obj_type_t no longer refers explicitly to
mp_stream_p_t but rather to an abstract "const void *protocol".  So there's
no longer any need to define mp_stream_p_t in obj.h and it can go with all
its associated definitions in stream.h.  Pretty much all users of this type
will already include the stream header.

py/obj.h

@@ -451,16 +451,6 @@ typedef struct _mp_buffer_p_t {
 bool mp_get_buffer(mp_obj_t obj, mp_buffer_info_t *bufinfo, mp_uint_t flags);
 void mp_get_buffer_raise(mp_obj_t obj, mp_buffer_info_t *bufinfo, mp_uint_t flags);
 
-// Stream protocol
-typedef struct _mp_stream_p_t {
-    // On error, functions should return MP_STREAM_ERROR and fill in *errcode (values
-    // are implementation-dependent, but will be exposed to user, e.g. via exception).
-    mp_uint_t (*read)(mp_obj_t obj, void *buf, mp_uint_t size, int *errcode);
-    mp_uint_t (*write)(mp_obj_t obj, const void *buf, mp_uint_t size, int *errcode);
-    mp_uint_t (*ioctl)(mp_obj_t obj, mp_uint_t request, uintptr_t arg, int *errcode);
-    mp_uint_t is_text : 1; // default is bytes, set this for text stream
-} mp_stream_p_t;
-
 struct _mp_obj_type_t {
     // A type is an object so must start with this entry, which points to mp_type_type.
     mp_obj_base_t base;

py/stream.h

@@ -62,6 +62,16 @@ struct mp_stream_seek_t {
 #define MP_SEEK_CUR (1)
 #define MP_SEEK_END (2)
 
+// Stream protocol
+typedef struct _mp_stream_p_t {
+    // On error, functions should return MP_STREAM_ERROR and fill in *errcode (values
+    // are implementation-dependent, but will be exposed to user, e.g. via exception).
+    mp_uint_t (*read)(mp_obj_t obj, void *buf, mp_uint_t size, int *errcode);
+    mp_uint_t (*write)(mp_obj_t obj, const void *buf, mp_uint_t size, int *errcode);
+    mp_uint_t (*ioctl)(mp_obj_t obj, mp_uint_t request, uintptr_t arg, int *errcode);
+    mp_uint_t is_text : 1; // default is bytes, set this for text stream
+} mp_stream_p_t;
+
 MP_DECLARE_CONST_FUN_OBJ_VAR_BETWEEN(mp_stream_read_obj);
 MP_DECLARE_CONST_FUN_OBJ_VAR_BETWEEN(mp_stream_read1_obj);
 MP_DECLARE_CONST_FUN_OBJ_VAR_BETWEEN(mp_stream_readinto_obj);