arm64: dts: renesas: r8a774a1: Add Cortex-A53 CPU cores

This patch adds definitions for L2 cache for the Cortex-A53 CPU
cores (512 KiB in size, organized as 32 KiB x 16 ways), adds
Cortex-A53 CPU cores (setting a total of 6 cores, 2 x Cortex-A57
+ 4 x Cortex-A53), and finally enables the performance monitor
unit for the Cortex-A53 cores on the R8A774A1 SoC.

Based on work done for r8a7796 SoC.

Signed-off-by: Biju Das <biju.das@bp.renesas.com>
Reviewed-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>