PCI: Rename extend_bridge_window() to adjust_bridge_window()

Rename extend_bridge_window() to adjust_bridge_window() to prepare for the
fact that the window will be able to shrink.  No functional change
intended.

Link: https://lore.kernel.org/r/PSXP216MB0438C47B3473D0C9DE531F18803C0@PSXP216MB0438.KORP216.PROD.OUTLOOK.COM


Signed-off-by: Nicholas Johnson <nicholas.johnson-opensource@outlook.com.au>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>