staging: r8188eu: Fix a smatch warnings in core/rtw_recv.c

Smatch reports the following:
drivers/staging/rtl8188eu/os_dep/recv_linux.c:227 rtw_recv_indicatepkt() warn: variable dereferenced before check 'precv_frame' (see line 139)

The test in this location is removed and added in the free routine.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>