s32g:pcie:ep: Make the driver compatible with the EP test framework

commit 6ec09971428bf839cb243a792f60cf7b7d1d5816 from
https://source.codeaurora.org/external/autobsps32/linux



Make the proper initialization from the S32G pcie driver.
Make configs PCI_S32GEN1_INIT_EP_BARS and PCI_EPF_TEST mutually exclusive
(as they control different test scenarios, and if PCI_S32GEN1_INIT_EP_BARS
is set, then epf fails to configure BARs).
Set custom BAR sizes when EPF is used.
Do not set class and revision in pcie driver when using EP test framework,
as it will be set from userspace via the filesystem.

Issue: ALB-4548

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