ARM: dts: mmp3: Use the MMP3 compatible string for /clocks

Clocks are in fact slightly different on MMP3. In particular, PLL2 is
fixed to a different frequency, there's an extra PLL3, and the GPU
clocks are configured differently.

Link: https://lore.kernel.org/r/20200419171157.672999-15-lkundrak@v3.sk


Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Cc: <stable@vger.kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>