zram: Fix sparse warnings

Fixes sparse warning:
zram_drv.c:666:6: warning: symbol 'zram_slot_free_notify' was not
declared. Should it be static?

Also, max_zpage_size is now size_t just to be consistent with data-type
of other variables maintaining sizes of various kinds.

Signed-off-by: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/zram/zram_drv.c

@@ -697,7 +697,8 @@ fail:
 	return ret;
 }
 
-void zram_slot_free_notify(struct block_device *bdev, unsigned long index)
+static void zram_slot_free_notify(struct block_device *bdev,
+				unsigned long index)
 {
 	struct zram *zram;
 

drivers/staging/zram/zram_drv.h

@@ -47,7 +47,7 @@ static const unsigned default_disksize_perc_ram = 25;
  * Pages that compress to size greater than this are stored
  * uncompressed in memory.
  */
-static const unsigned max_zpage_size = PAGE_SIZE / 4 * 3;
+static const size_t max_zpage_size = PAGE_SIZE / 4 * 3;
 
 /*
  * NOTE: max_zpage_size must be less than or equal to: