qualcommax: ipq50xx: fix ECC strength for Linksys MR5500

qualcommax: ipq50xx: fix ECC strength for Linksys MR5500

Commit fc3ff2af0c57504a2e03d635692396c5bb099f17 introduced reading
ECC strength from the device tree. Linksys MR5500 uses the mx-base dtsi
which was originally developed for Linksys MX2000 and MX5500 where the
ECC strength is set to 8. Correct this and set it to strength of 4 as
per the NAND specs for Gigadevice GD5F2GQ5REYIH.

Signed-off-by: George Moussalem <george.moussalem@outlook.com>
Link: https://github.com/openwrt/openwrt/pull/18672
Signed-off-by: Robert Marko <robimarko@gmail.com>