The code looks normal. What looks wrong is the connection you have. There are swapped RX and TX pins between MCU and PHY. But maybe it is just mistake on the SCH.
If the connection is correct, means PB0/PC10 to TXD and PB1/PC3 to RXD then you can try this:
- set weak pull ups on RX pins
SIU.PCR[35].R = 0x0103;
SIU.PCR[17].R = 0x0103;
- look at ECR and ESR registers to know if there is any error
BR.
Petr