rtlwifi: Fix incorrect return from rtl_ps_enable_nic()

rtl_ps_enable_nic() is called from loops that will loop until this function returns true or a
maximum number of retries is performed.

hw_init() returns non-zero on error. In that situation return false to
restore the original design intent to retry hw init when it fails.

Signed-off-by: Olivier Langlois <olivier@trillion01.com>
Cc: Stable <stable@vger.kernel.org>
Acked-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>