Support for RTL838x based managed switches

Thanks! Yeah I failed at adding JG927A and JG928A sections properly into the wiki.

Perhaps we discuss this more here:

I'm not game to try to add an hwdata page by creating it manually in the right spot as that looks to be against the wiki rules.

I'm done for today though.
https://openwrt.org/toh/hwdata/3com/3com_1920-48g_jg927a_hng7a-ha0015
https://openwrt.org/toh/hwdata/please_select/please_select_1920-48g-poe_370w_jg928a_hngza-ha0016

One is now "3com" and one is "please select" =P