fs: Mark function as static in exofs/super.c

Mark function as static in exofs/super.c because it is not used outside
this file.

This also eliminates the following warning in exofs/super.c:
 fs/exofs/super.c:546:5: warning: no previous prototype \
 for __alloc_dev_table[-Wmissing-prototypes]
Signed-off-by: Rashika Kheria <rashika.kheria@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>

fs/exofs/super.c

@@ -543,7 +543,7 @@ static int exofs_devs_2_odi(struct exofs_dt_device_info *dt_dev,
 	return !(odi->systemid_len || odi->osdname_len);
 }
 
-int __alloc_dev_table(struct exofs_sb_info *sbi, unsigned numdevs,
+static int __alloc_dev_table(struct exofs_sb_info *sbi, unsigned numdevs,
 		      struct exofs_dev **peds)
 {
 	struct __alloc_ore_devs_and_exofs_devs {