PCI: dwc: Wait for link up only if link is 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.

Link: https://lore.kernel.org/r/20230412093425.3659088-1-ajayagarwal@google.com


Tested-by: Will McVicker <willmcvicker@google.com>
Signed-off-by: Sajid Dalvi <sdalvi@google.com>
Signed-off-by: Ajay Agarwal <ajayagarwal@google.com>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>