ab8500_fg: Fix some build warnings on x86_64

Noticed the following warnings:

  CC      drivers/power/ab8500_fg.o
drivers/power/ab8500_fg.c: In function 'charge_full_store':
drivers/power/ab8500_fg.c:2258:2: warning: format '%d' expects argument of type 'int', but argument 4 has type 'ssize_t' [-Wformat]
drivers/power/ab8500_fg.c: In function ‘charge_now_store’:
drivers/power/ab8500_fg.c:2280:2: warning: format '%d' expects argument of type 'int', but argument 4 has type 'ssize_t' [-Wformat]

This patch fixes the issues.

Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
diff --git a/drivers/power/ab8500_fg.c b/drivers/power/ab8500_fg.c
index eaf149e..c22f2f0 100644
--- a/drivers/power/ab8500_fg.c
+++ b/drivers/power/ab8500_fg.c
@@ -2255,7 +2255,7 @@
 
 	ret = strict_strtoul(buf, 10, &charge_full);
 
-	dev_dbg(di->dev, "Ret %d charge_full %lu", ret, charge_full);
+	dev_dbg(di->dev, "Ret %zd charge_full %lu", ret, charge_full);
 
 	if (!ret) {
 		di->bat_cap.max_mah = (int) charge_full;
@@ -2277,7 +2277,7 @@
 
 	ret = strict_strtoul(buf, 10, &charge_now);
 
-	dev_dbg(di->dev, "Ret %d charge_now %lu was %d",
+	dev_dbg(di->dev, "Ret %zd charge_now %lu was %d",
 		ret, charge_now, di->bat_cap.prev_mah);
 
 	if (!ret) {