clk: keystone: TI_SCI_PROTOCOL is needed for clk driver

CONFIG_COMPILE_TEST allows building a configuration without
TI_SCI_PROTOCOL, which then fails to link:

drivers/clk/keystone/sci-clk.o: In function `ti_sci_clk_probe':
sci-clk.c:(.text.ti_sci_clk_probe+0x4c): undefined reference to `devm_ti_sci_get_handle'

This makes it a hard dependency. Right now, that means we can't
actually compile-test the driver unless ARCH_KEYSTONE is set as
well, but we can fix that by allowing TI_MESSAGE_MANAGER to
be selected for COMPILE_TEST as well.

Fixes: b745c079 ("clk: keystone: Add sci-clk driver support")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>