cxl: Remove unnecessary cxl_pci_window_alignment()

cxl_pci_window_alignment() is referenced only via the struct
pci_controller_ops.window_alignment function pointer, and only in the
powerpc implementation of pcibios_window_alignment().

pcibios_window_alignment() defaults to returning 1 if the function pointer
is NULL, which is the same was what cxl_pci_window_alignment() does.

cxl_pci_window_alignment() is unnecessary, so remove it.  No functional
change intended.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Frederic Barrat <fbarrat@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20221205223231.1268085-1-helgaas@kernel.org