rtl_bt: Add firmware v2 file for RTL8852C

This firmware is submitted for RTL8852C BT USB I/F.

Release version is 0x040D_7225

Due to the follow-up RTL8852C firmware patch is format v2,
the RTL8852C BT USB firmware updates will be launched
with rtl8852cu_fw_v2.bin.

Suggested-by: Juerg Haefliger <juerg.haefliger@canonical.com>
Signed-off-by: Hilda Wu <hildawu@realtek.com>
Signed-off-by: Josh Boyer <jwboyer@kernel.org>