UBIFS: push empty flash hack down

We have a hack which forces the amount of flash space to be
equivalent to 'c->blocks_cnt' in case of empty FS. This is
to make users happy and see '%0' used in 'df' when they
mount an empty FS. This hack is not needed in
'ubifs_calc_available()', but it is only needed the caller,
in 'ubifs_budg_get_free_space()'. So push it down there.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

fs/ubifs/super.c

@@ -649,8 +649,6 @@ static int init_constants_late(struct ubifs_info *c)
 	 *
 	 * Subtract the LEB reserved for GC and the LEB which is reserved for
 	 * deletions.
-	 *
-	 * Review 'ubifs_calc_available()' if changing this calculation.
 	 */
 	tmp64 = c->main_lebs - 2;
 	tmp64 *= (uint64_t)c->leb_size - c->dark_wm;