fs: pipe: reveal missing function protoypes

A couple of functions from fs/pipe.c are used both internally
and for the watch queue code, but the declaration is only
visible when the latter is enabled:

fs/pipe.c:1254:5: error: no previous prototype for 'pipe_resize_ring'
fs/pipe.c:758:15: error: no previous prototype for 'account_pipe_buffers'
fs/pipe.c:764:6: error: no previous prototype for 'too_many_pipe_buffers_soft'
fs/pipe.c:771:6: error: no previous prototype for 'too_many_pipe_buffers_hard'
fs/pipe.c:777:6: error: no previous prototype for 'pipe_is_unprivileged_user'

Make the visible unconditionally to avoid these warnings.

Fixes: c73be61c ("pipe: Add general notification queue support")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Message-Id: <20230516195629.551602-1-arnd@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>