clk: clk-imx8qm: Add LPUART IPG entries

Since commit cc7df0b9 ("serial: lpuart: Enable IPG clock")
the apalis-imx8qm board no longer boots.

The reason is that the imx8qm clock driver does not handle the
LPUART IPG clocks inside get_rate(), set_rate() and enable() functions.

Fix the boot regression by adding the LPUART IPG entries.

Fixes: cc7df0b9 ("serial: lpuart: Enable IPG clock")
Reported-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>