clk: COMMON_CLK_LAN966X should depend on SOC_LAN966

The LAN966x Generic Clock Controller is only present on Microchip
LAN966x SoCs.  Hence add a dependency on SOC_LAN966, to prevent asking
the user about this driver when configuring a kernel without LAN966x SoC
support.

Fixes: 54104ee0

 ("clk: lan966x: Add lan966x SoC clock driver")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/eb102eae05e5667b9bd342a0c387f7f262d24bda.1645716471.git.geert+renesas@glider.be
Reviewed-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>