clk: Kconfig: Name RK818 in Kconfig for COMMON_CLK_RK808

The RK808 and RK818 PMICs are using a similar register map.
We can reuse the clk driver for the RK818 PMIC. So let's add
the RK818 in the Kconfig description.

Signed-off-by: Wadim Egorov <w.egorov@phytec.de>
Acked-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Michael Turquette <mturquette@baylibre.com>
Link: lkml.kernel.org/r/1464850228-17244-4-git-send-email-w.egorov@phytec.de