Revert "apm821xx: rename pciex to pcie"

Revert "apm821xx: rename pciex to pcie"

This reverts commit 66a7e04e9e10247978c301a679428cbfc001e6ea.

Doing so makes the u-boot unable to find the node for this pcie
controller and disable it on mx60, resulting boot failure, as reported
in https://github.com/openwrt/openwrt/issues/21649 .

If we keep on treating mx60 and mx60w the same target, we might have
to endure the warning which 66a7e04 wants to eliminate.

Signed-off-by: Edward Chow <equu@openmail.cc>
Link: https://github.com/openwrt/openwrt/pull/21941
Signed-off-by: Robert Marko <robert.marko@sartura.hr>