lib/idr.c: document that ida_simple_{get,remove}() are deprecated

These two functions are deprecated.  Users should call ida_alloc() or
ida_free() respectively instead.  Add documentation to this effect until
the macro can be removed.

Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Tri Vo <trong@android.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox <willy@infradead.org>
Link: https://lkml.kernel.org/r/20200910055246.2297797-2-swboyd@chromium.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/idr.h

@@ -314,6 +314,10 @@ static inline void ida_init(struct ida *ida)
 	xa_init_flags(&ida->xa, IDA_INIT_FLAGS);
 }
 
+/*
+ * ida_simple_get() and ida_simple_remove() are deprecated. Use
+ * ida_alloc() and ida_free() instead respectively.
+ */
 #define ida_simple_get(ida, start, end, gfp)	\
 			ida_alloc_range(ida, start, (end) - 1, gfp)
 #define ida_simple_remove(ida, id)	ida_free(ida, id)