ARM: rmobile: gen2: Enable ACTLR[0] (Enable invalidates of BTB) to facilitate CVE_201...

ARM: rmobile: gen2: Enable ACTLR[0] (Enable invalidates of BTB) to facilitate CVE_2017-5715 WA in OS

Enable CVE_2017_5715 mitigation on CPU0 on R-Car H2, M2W, M2N, V2H,
which all contain Cortex-A15 cores. R-Car E2 contains only Cortex-A7
cores and is not affected. Without this enabled, Linux kernel reports:

  CPU0: Spectre v2: firmware did not set auxiliary control register IBE bit, system vulnerable

With this enabled, Linux kernel reports:

  CPU0: Spectre v2: using ICIALLU workaround

NOTE: This by itself does not enable the workaround for other CPUs
      than CPU0 and may require additional kernel patches for the
      other CPUs in SMP configurations.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Nishanth Menon <nm@ti.com>
Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>