defconfig: msm: enable PCIe endpoint driver for sdxpoorwills

PCIe endpoint driver enables PCIe controller in PCIe endpoint mode
to set up the link with PCIe root complex side.

Change-Id: I38bdf3dfaa5da2d50752ca90fc6eb5b4bd2a4e0e
Signed-off-by: Yan He <yanhe@codeaurora.org>