net: stream: add description for sk_stream_write_space()

Add a proper description for the sk_stream_write_space() function as
previously marked by a FIXME comment.
No functional changes.

Signed-off-by: Suchit Karunakaran <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

net/core/stream.c

···
 
 /**
  * sk_stream_write_space - stream socket write_space callback.
- * @sk: socket
+ * @sk: pointer to the socket structure
  *
- * FIXME: write proper description
+ * This function is invoked when there's space available in the socket's
+ * send buffer for writing. It first checks if the socket is writable,
+ * clears the SOCK_NOSPACE flag indicating that memory for writing
+ * is now available, wakes up any processes waiting for write operations
+ * and sends asynchronous notifications if needed.
  */
 void sk_stream_write_space(struct sock *sk)
 {