HSI: omap-ssi: add COMMON_CLK dependency

Enabling the omap ssi driver without COMMON_CLK results in a build failure:

drivers/hsi/controllers/omap_ssi_core.c: In function 'ssi_clk_event':
drivers/hsi/controllers/omap_ssi_core.c:304:7: error: 'PRE_RATE_CHANGE' undeclared (first use in this function)

This adds a Kconfig dependency to avoid the invalid configuration.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 4bcf7414 ("HSI: omap-ssi: add clk change support")
Signed-off-by: Sebastian Reichel <sre@kernel.org>