habanalabs/gaudi: remove pcie_en strap toggle

Since the very large grace period is over and this functionality
prevents us to implement the new reset sequence and apply security
settings, we need to remove the code toggling the PCIE_EN bit in the
straps register.
Remove it for good.

Signed-off-by: Igor Grinberg <igrinberg@habana.ai>
Reviewed-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>