staging: rtl8188eu: Replace function name with __func__

Fix the following checkpatch warning:
	WARNING: Prefer using '"%s...", __func__' to using 'rtw_get_bcn_info', this function's name, in a string

Signed-off-by: Brooke Basile <brookebasile@gmail.com>
Link: https://lore.kernel.org/r/20200629173711.5158-1-brookebasile@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>