clk: mediatek: clk-mt8173-apmixedsys: Fix iomap not released issue

In case of error after of_ioremap() the resource must be released:
call iounmap() where appropriate to fix that.

Fixes: 41138fbf ("clk: mediatek: mt8173: Migrate to platform driver and common probe")
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20230615122051.546985-4-angelogioacchino.delregno@collabora.com


Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>