rtc: pcf8563: fix output clock rate

rtc: pcf8563: fix output clock rate

[ Upstream commit a3350f9c57ffad569c40f7320b89da1f3061c5bb ]

The pcf8563_clkout_recalc_rate function erroneously ignores the
frequency index read from the CLKO register and always returns
32768 Hz.

Fixes: a39a6405d5f9 ("rtc: pcf8563: add CLKOUT to common clock framework")
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>