MIPS: Kconfig: Enable common clock framework for Malta and SEAD3

Now that we're ready to enable COMMON_CLK for GIC platforms do so for
Malta and SEAD3.  The only other user of the GIC Pistachio does already
do so.

[ralf@linux-mips.org: Rewrite the commit message because applied in the
right order there is no breakage thus no fix required.]

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Cc: Ezequiel Garcia <ezequiel.garcia@imgtec.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/11038/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
