dt-bindings: imx: Add clock binding for i.MXRT1050

Add the clock binding doc for i.MXRT1050.

Signed-off-by: Giulio Benetti <giulio.benetti@benettiengineering.com>
Signed-off-by: Jesse Taube <Mr.Bossman075@gmail.com>
[Jesse: added clocks from IMXRT1050_CLK_IPG_PDOF to
IMXRT1050_CLK_DMA_MUX and moved IMXRT1050_CLK_END on]
Acked-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20220111215415.2075257-4-Mr.Bossman075@gmail.com
Signed-off-by: Abel Vesa <abel.vesa@nxp.com>