wifi: rtlwifi: fix init_sw_vars leak when probe fails

If ieee80211_register_hw fails, the memory allocated for the firmware will
not be released. Call deinit_sw_vars as the function that undoes the
allocationes done by init_sw_vars.

Fixes: cefe3dfd ("rtl8192cu: Call ieee80211_register_hw from rtl_usb_probe")
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20241107133322.855112-5-cascardo@igalia.com