fs/netfs: remove unused flag NETFS_RREQ_BLOCKED

fs/netfs: remove unused flag NETFS_RREQ_BLOCKED

NETFS_RREQ_BLOCKED was added by commit 016dc8516aec ("netfs: Implement
unbuffered/DIO read support") but has never been used either.  Without
NETFS_RREQ_BLOCKED, NETFS_RREQ_NONBLOCK makes no sense, and thus can
be removed as well.

Signed-off-by: Max Kellermann <max.kellermann@ionos.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/20250519134813.2975312-12-dhowells@redhat.com
cc: Paulo Alcantara <pc@manguebit.com>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>