net: stmmac: Fix PCI module removal leak

Since commit b7d0f08e, the enable / disable of PCI device is not
managed which will result in IO regions not being automatically unmapped.
As regions continue mapped it is currently not possible to remove and
then probe again the PCI module of stmmac.

Fix this by manually unmapping regions on remove callback.

Changes from v1:
- Fix build error

Cc: Joao Pinto <jpinto@synopsys.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Fixes: b7d0f08e ("net: stmmac: Fix WoL for PCI-based setups")
Signed-off-by: Jose Abreu <joabreu@synopsys.com>
Signed-off-by: David S. Miller <davem@davemloft.net>