ANDROID: PCI: dwc: Export symbols for ep driver

Several symbols in DesignWare PCI Core driver are used
to support PCIe controller work at Endpoint Mode.
Export them to support such driver built as module.

Bug: 159736148
Signed-off-by: Jindong Yue <jindong.yue@nxp.com>
Change-Id: I2c77bfbfbec750ecdf21f0cd1bbb20fe339a2f0c