ipq806x: mr42/mr52: fix PCIe ports

ipq806x: mr42/mr52: fix PCIe ports

All three PCIe ports are reported non working on Meraki MR42/MR52 boards
since kernel 6.1 with the issue of PCIe PHY link never coming up thus
no WLAN cards are available on the boards.

After debugging it seems that PCIe worked on 5.15 and older purely by
accident as device DTS was using /delete-property/ perst-gpios; in each
of the 3 PCIe nodes but there was no "perst-gpios" property in the SoC DTSI
as it was still using the older "perst-gpio" property so it was not getting
removed from the device DTS.

However, in kernel 6.1 commit ("ARM: dts: qcom-*: replace deprecated
perst-gpio with perst-gpios") updated all Qualcomm DTS-es to use the newer
"perst-gpios" and thus once ipq806x moved to 6.1 PCIe stopped working as
now that property was being dropped from the device DTS.

So, since the removal of PERST pins seems to have been wrong from the start
lets drop the property removal from MR42/MR52.

Fixes: #15408
Link: https://github.com/openwrt/openwrt/pull/15509
Signed-off-by: Robert Marko <robimarko@gmail.com>