ramips: restore CONFIG_PAGE_BLOCK_MAX_ORDER=10 for 6.18

ramips: restore CONFIG_PAGE_BLOCK_MAX_ORDER=10 for 6.18

Restore CONFIG_PAGE_BLOCK_MAX_ORDER=10 in ramips 6.18 config fragments
to fix build failures where PAGE_BLOCK_MAX_ORDER was undefined.

Support for Linux 6.18 on ramips was added after this OpenWrt change:
https://github.com/openwrt/openwrt/commit/ac0cb87a453698efc6c812e4f27cadbeb208f14e.
Before that integration, the kernel option CONFIG_PAGE_BLOCK_MAX_ORDER=10
was provided in target/linux/generic/config-6.18 and applied broadly.
After the ramips 6.18 integration the generic fragment no longer supplied
this option for ramips targets, which caused some backported code paths
and drivers to assume PAGE_BLOCK_MAX_ORDER was defined and led
to compilation failures.

Signed-off-by: Mieczyslaw Nalewaj <namiltd@yahoo.com>
Link: https://github.com/openwrt/openwrt/pull/22831
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>