clk: mediatek: Fix apmixedsys clock registration

The size of clk_data should be the same as CLK_APMIXED_NR_CLK
instead of ARRAY_SIZE(plls). CLK_APMIXED_* is numbered from 1, so
CLK_APMIXED_NR_CLK will be greater than ARRAY_SIZE(plls).

Signed-off-by: James Liao <jamesjj.liao@mediatek.com>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>