ramips: remove obsolete SPI flash nodes after kernel fix

ramips: remove obsolete SPI flash nodes after kernel fix

Remove incomplete SPI flash definitions from affected device tree files.
These fragments only defined address-cells and size-cells without any
actual flash configuration (partitions, compatible string, etc.).

After applying openwrt/openwrt#20942 ("kernel: of: fix bad cell count error
for SPI flash node"), the kernel properly handles SPI flash nodes without
requiring these incomplete definitions in device-specific DTS files.

This cleanup eliminates unnecessary code that was likely a workaround for
the previous kernel issue.

Signed-off-by: Mieczyslaw Nalewaj <namiltd@yahoo.com>
Link: https://github.com/openwrt/openwrt/pull/22036
Signed-off-by: Robert Marko <robimarko@gmail.com>
(cherry picked from commit 313d56366448d8c2ca12daba7725fdd848057d98)