PCI: sky1: Fix missing cleanup of ECAM config on probe failure

PCI: sky1: Fix missing cleanup of ECAM config on probe failure

When devm_kzalloc() for reg_off fails, the code returns -ENOMEM without
freeing pcie->cfg, which was allocated earlier by pci_ecam_create().

Add the missing pci_ecam_free() call to properly release the allocated ECAM
configuration window on this error path.

Fixes: a0d9f2c08f45 ("PCI: sky1: Add PCIe host support for CIX Sky1")
Signed-off-by: Felix Gu <ustc.gu@gmail.com>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Reviewed-by: Hans Zhang <18255117159@163.com>
Link: https://patch.msgid.link/20260324-sky1-v1-1-6a00cb2776b6@gmail.com