ARM: dts: meson8: add more L2 cache settings

Amlogic's vendor kernel prints these PL310 L2 cache controller settings
during boot:
  8 ways, 4096 sets, CACHE_ID 0x4100a0c9,  Cache size: 1048576 B
  AUX_CTRL 0x7ec80001, PERFETCH_CTRL 0x71000007, POWER_CTRL  0x00000000
  TAG_LATENCY 0x00000111, DATA_LATENCY 0x00000222

Add the "prefetch-data", "prefetch-instr" and "arm,shared-override"
properties to get the same L2 cache controller configuration as the
vendor kernel.
Two differences still remain:
- L310_AUX_CTRL_NS_INT_CTRL is currently not supported by the cache-l2x0
driver
- bit 23 is set by the vendor kernel, but this is defined in cache-l2x0.h

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Tested-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>