clk: mediatek: mt8192: Move apmixedsys clock driver to its own file

This is the last man standing in clk-mt8192.c that won't allow us to
use the module_platform_driver() macro, and for *no* good reason.
Move it to clk-mt8192-apmixedsys.c and while at it, also add a
.remove() callback for it.

Also, since the need for "clk-mt8192-simple" and "clk-mt8192" was
just due to them being in the same file and probing different clocks,
and since now there's just one platform_driver struct per file, it
seemed natural to rename the `-simple` variant to just "clk-mt8192".

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Tested-by: Miles Chen <miles.chen@mediatek.com>
Tested-by: Chen-Yu Tsai <wenst@chromium.org>
Link: https://lore.kernel.org/r/20230306140543.1813621-48-angelogioacchino.delregno@collabora.com


Signed-off-by: Stephen Boyd <sboyd@kernel.org>