Update PDO assign requirement and config logic

- Remove PDO assign requirement from README.
- Check enable_pdo_assign before configuring PDOs in ec_slave_config.

README.md

@@ -39,7 +39,6 @@ CherryECAT is a tiny and beautiful, high real-time and low-jitter EtherCAT maste
 
 - **Slave**
 	- Must support COE
-	- Must support PDO assign
 	- Must support sdo complete access
 	- SII must have sync manager information
 

README_zh.md

@@ -39,7 +39,6 @@ CherryECAT 是一个小而美的、高实时性、低抖动的 EtherCAT 主机
 
 - 从站
 	- 必须支持 COE
-	- 必须支持 PDO assign
 	- 必须支持 sdo complete access
 	- SII 必须携带 sync manager 信息
 

src/ec_slave.c

@@ -530,7 +530,7 @@ static int ec_slave_config(ec_master_t *master, ec_slave_t *slave)
         return ret;
     }
 
-    if (slave->config) {
+    if (slave->config && slave->sii.general.coe_details.enable_pdo_assign) {
         uint32_t data;
 
         /* Config PDO assignments for 0x1c12, 0x1c13