clk: mvebu: Move corediv config to mvebu config

The core clock does not depend on corediv, so enabling corediv
based on the clock is not really correct.  Move the corediv
config option from the clock driver Kconfig to the mvebu Kconfig
so that it can be enabled by the MACH option instead.

This also enables corediv on Armada 375 and 38X, which was
previously missing.

Signed-off-by: Kevin Smith <kevin.smith@elecsyscorp.com>
Cc: Michael Turquette <mturquette@baylibre.com>
Cc: Stephen Boyd <sboyd@codeaurora.org>
Cc: Gregory CLEMENT <gregory.clement@free-electrons.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>