[FIX] account_asset: inconsistencies deferred revenues and assets

The following configuration leads to different results:
- Deferred revenue: 12 entries, 1/month, prorata temporis, 1000€,
  date 15th of October
- Asset: 12 entries, 1/month, prorata temporis, 1000€, linear, date
  15th of October

Deferred revenues and assets should give identical results.

opw-690034

addons/account_asset/account_asset.py

@@ -126,7 +126,7 @@ def _compute_board_amount(self, sequence, residual_amount, amount_to_depr, undon
         else:
             if self.method == 'linear':
                 amount = amount_to_depr / (undone_dotation_number - len(posted_depreciation_line_ids))
-                if self.prorata and self.category_id.type == 'purchase':
+                if self.prorata:
                     amount = amount_to_depr / self.method_number
                     if sequence == 1:
                         days = (self.company_id.compute_fiscalyear_dates(depreciation_date)['date_to'] - depreciation_date).days + 1
@@ -147,7 +147,7 @@ def _compute_board_undone_dotation_nb(self, depreciation_date, total_days):
             while depreciation_date <= end_date:
                 depreciation_date = date(depreciation_date.year, depreciation_date.month, depreciation_date.day) + relativedelta(months=+self.method_period)
                 undone_dotation_number += 1
-        if self.prorata and self.category_id.type == 'purchase':
+        if self.prorata:
             undone_dotation_number += 1
         return undone_dotation_number