s32gen1:pcie: Use list to store EP instances

commit e2fae65509b9696eef3c2acfaa33509cf71c9b58 from
https://source.codeaurora.org/external/autobsps32/linux



Remove the local pointer to one EP instance, and use a list
instead with proper add/remove mechanism.
This fixes a memory leak for the case when both controllers
are configured as EndPoints, and allows both of them to be
configured from user space.

Issue: ALB-7907

Signed-off-by: Ionut Vicovan <Ionut.Vicovan@nxp.com>
Signed-off-by: Zhantao Tang <zhantao.tang@windriver.com>