realtek: dsa: rtl839x: Fix incorrect drop counter names

realtek: dsa: rtl839x: Fix incorrect drop counter names

The counter names "CFM" and "VLAN_IGR_FLTR" were not separated by a comma
in the `rtl839x_drop_cntr` array. As result, these two headers were merged
to a single header "CFMVLAN_IGR_FLTR" and everything after that was shifted
by one. The last name (for the 45th counter) was also not defined and was
therefore accessing data outside the array.

Fixes: 1cfd45ae0bad ("realtek: Add debugfs support for RTL9300")
Signed-off-by: Sven Eckelmann <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/20905
Signed-off-by: Robert Marko <[email protected]>