clk: mmp2: Check for MMP3

The MMP3's are similar enough to MMP2, but there are differencies, such
are more clocks available on the newer model. We want to tell which
platform are we on.

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Link: https://lkml.kernel.org/r/20200309194254.29009-8-lkundrak@v3.sk


Signed-off-by: Stephen Boyd <sboyd@kernel.org>