staging:rtl8188eu Use __func__ instead of function name

This patch makes use of predefined identifier __func__ inorder to clear
the warning: Prefer using '"%s...", __func__' to using 'update_bmc_sta',
this function's name, in a string

Signed-off-by: Janani Sankara Babu <jananis37@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>