pcie: host: tegra: change prsnt override mechanism

pcie: host: tegra: change prsnt override mechanism

overrides prsnt control based on card detection through
GPIO values that reflect PRSNT status
If the platform doesn't support PRSNT through GPIO, software
overrides will be enabled always

Bug 200067556

Change-Id: I43b732ead3bab7dfbe1fcb910dc269c450b34230
Signed-off-by: Vidya Sagar <vidyas@nvidia.com>
Reviewed-on: http://git-master/r/667029
Reviewed-by: Automatic_Commit_Validation_User
GVS: Gerrit_Virtual_Submit
Reviewed-by: Laxman Dewangan <ldewangan@nvidia.com>