rtlwifi: rtl8192cu: Update the power index registers

commit 9806eacf5de27ab01d680c5d75c92a3a89734e4f upstream.

This patch uses the newly introduced power index register routines.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>