ARM: dts: r8a7794: fix PWM clock parent

ARM: dts: r8a7794: fix PWM clock parent

When removing the non-existing thermal clock I forgot to remove its
parent from the node's "clocks" property  -- this led to a wrong PWM
clock's parent clock.

Fixes: 2a29f9d6fea8 ("ARM: dts: r8a7794: add MSTP5 clocks")
Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>