clk: imx7ulp: Fix watchdog2 clock name typo

There is a typo in the watchdog2 clock name.

Fix it by changing it to "wdg2".

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Reviewed-by: Abel Vesa <abel.vesa@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>