ANDROID: PCI: dwc: Wait for the link only if it has been started

In dw_pcie_host_init() regardless of whether the link has been
started or not, the code waits for the link to come up. Even in
cases where start_link() is not defined the code ends up spinning
in a loop for 1 second. Since in some systems dw_pcie_host_init()
gets called during probe, this one second loop for each pcie
interface instance ends up extending the boot time.

Wait for the link up in only if the start_link() is defined.

The patch submitted to the upstream kernel (see link below) was not
accepted due to no upstream user.

The change here is a simplified version of that patch, which will wait
for a link only if start_link ops has been defined.

Also, this patch was already applied before in
https://r.android.com/2548250 but the functionality was lost after
https://lore.kernel.org/all/20220624143428.8334-14-Sergey.Semin@baikalelectronics.ru/
was pulled in from the LTS merge.

This patch restores the functionality (of removing the delay) which was
lost during the LTS merge.

Bug: 315052790
Bug: 328536505
Link: https://lore.kernel.org/all/20240112093006.2832105-1-ajayagarwal@google.com/


Change-Id: I4e8d00f6195062728417e41ddd51072880676920
Signed-off-by: Sajid Dalvi <sdalvi@google.com>
(cherry picked from commit 288abb8b)