drivers: pci: imx: fix imx_pcie_remove function

We have at least a minor count of boards, that failed to re-initialize
PCI express in the Linux kernel. Typical failure rate is 20% on affected
boards. This is mitigated by commit 6ecbe137 ("drivers: pci: imx:
add imx_pcie_remove function").

However, at least on some i.MX6 custom boards, when calling
assert_core_reset() as part of the first-time PCIe init, read access
to PCIE_PL_PFLR simply hangs. Surround this readl() with
imx_pcie_fix_dabt_handler() does not help. For this reason, the forced
LTSSM detection is only used on the second assert_core_reset() that is
called shorly before starting the Linux kernel.

Signed-off-by: Sven-Ola Tuecke <sven-ola.tuecke@numberfour.eu>
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Tested-by: David Müller <d.mueller@elsoft.ch>