realtek: fix Linksys LGS328C dts memory definition
RTL930x devices have highmem starting address at 0x20000000.
The Linksys LGS328C highmem definition is wrongly shared with
the larger LGS352C RTL931x model and starts at 0x90000000.
Fix it by splitting the definition.
Fixes: 853d73f ("realtek: add support for Linksys LGS328C")
Signed-off-by: Markus Stockhausen <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/21262
Signed-off-by: Hauke Mehrtens <[email protected]>