lib min_heap: Switch to size_t

size_t is the correct type for a count of objects that can fit in
memory: this also means heaps now have the same memory layout as darrays
(fs/bcachefs/darray.h), and darrays can be used as heaps.

Cc: Kuan-Wei Chiu <[email protected]>
Cc: Ian Rogers <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Coly Li <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Signed-off-by: Kent Overstreet <[email protected]>

include/linux/min_heap.h

@@ -15,8 +15,8 @@
  */
 #define MIN_HEAP_PREALLOCATED(_type, _name, _nr)	\
 struct _name {	\
-	int nr;	\
-	int size;	\
+	size_t nr;	\
+	size_t size;	\
 	_type *data;	\
 	_type preallocated[_nr];	\
 }