msm: pcie: Remove saving/restoring Endpoint config space

PCIe Endpoint driver is responsible for saving and restoring the
config space of Endpoint during suspend/resume. Thus, remove this
functionality in PCIe bus driver.

Change-Id: I7016e89cc2ce173cfb40858dcb3f756716d80667
Signed-off-by: Yan He <yanhe@codeaurora.org>