clk: mediatek: don't select clk-mt8192 for all ARM64 builds

clk: mediatek: don't select clk-mt8192 for all ARM64 builds

This option defaults to y for ARCH64 meaning it's built even if we don't
want anything related to mediatek. Make the default condition stricter
and only build it if ARCH_MEDIATEK is selected.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Reviewed-by: Brian Masney <bmasney@redhat.com>
Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>