linux-phytec-ti

ARM: dts: am437x-gp-evm: Fix OV2659 xvclk entry to use audio-mstrclk

On am437x-gp-evm the OV2659 sensor clock source is coming directly
from the board's 12MHz crystal. In order to model this properly
a fixed-rate clock object is also created and labeled audio_mstrclk
to match the schematics.

Signed-off-by: Benoit Parrot <bparrot@ti.com>