ramips: lower re305-v3 spi-max-frequency

ramips: lower re305-v3 spi-max-frequency

Fix flash I/O instability observed in newer devices with cFeon
QH64A-104HIP (detected as en25qh64).

Ref: https://forum.openwrt.org/t/support-for-tp-link-re305-v3/75893/91

Reported-by: Dimitri Souza <dimitri.souza@gmail.com>
Tested-by: Dimitri Souza <dimitri.souza@gmail.com>
Signed-off-by: Joe Mullally <jwmullally@gmail.com>
[alter commit-message - target master]
Signed-off-by: David Bauer <mail@david-bauer.net>
(cherry picked from commit 2122c80b321d439cf8b669ae26fcfeec605cf2cc)