arm64: Kconfig.platforms: Re-organized Broadcom menu

[Naresh Kamboju]

From: lkft at linaro.org

LKFT test farm found that Linux next-20220906 onwards the Broadcom DTB
builds are not happening. And after bisecting we found this patch is
the reason [1].

Reported-by: Linux Kernel Functional Testing <lkft at linaro.org>

FYI, We have not changed any kernel configs.
[1] http://ix.io/49Wq


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