arm64: dts: renesas: r8a7795: Update OPPs to support CA53 dfs

Describe frequencies, other than the default for CA53 cores.  This is a
pre-requisite for using providing alternative frequencies for use with
CPUFreq with these cores.

Signed-off-by: Dien Pham <dien.pham.ry@renesas.com>
Signed-off-by: Takeshi Kihara <takeshi.kihara.df@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>