apps/wallet+apps/ethereum: fix formatting of amounts (avoid using float)

src/apps/ethereum/layout.py

@@ -48,4 +48,8 @@ def format_amount(value, token, chain_id):
         decimals = 18
         suffix = networks.suffix_by_chain_id(chain_id)
 
-    return '%s %s' % (value // 10 ** decimals, suffix)
+    d = pow(10, decimals)
+    value = ('%d.%0*d' % (value // d , decimals, value % d)).rstrip('0')
+    if value.endswith('.'):
+        value += '0'
+    return '%s %s' % (value, suffix)

src/apps/wallet/sign_tx/layout.py

@@ -8,7 +8,11 @@ from apps.common.confirm import hold_to_confirm
 
 
 def format_amount(amount, coin):
-    return '%s %s' % (amount / 1e8, coin.coin_shortcut)
+    d = pow(10, 8)
+    amount = ('%d.%08d' % (amount // d , amount % d)).rstrip('0')
+    if amount.endswith('.'):
+        amount += '0'
+    return '%s %s' % (amount, coin.coin_shortcut)
 
 
 def split_address(address):