clk: imx: clk-imx6ul: The i.mx6ul has no aips_tz3 clock

The clock was mapped on CG15 (gpio2_clocks) in the CCRG0 register.

Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Robin van der Gracht <robin@protonic.nl>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Michael Turquette <mturquette@baylibre.com>