arm: dts: sync am33xx-clocks with Linux 5.9-rc7

The commit 6337d53f ("arm: dts: sync am33xx with Linux 5.9-rc7")
synchronized the am33xx-clocks.dtsi file with Linux 5.9-rc7 with the
exception of two nodes. I think I was wrong and it is better to keep
the two files similar and possibly make changes to the *-u-boot.dtsi
files.

Signed-off-by: Dario Binacchi <dariobin@libero.it>