[ARM] Add support for ARM Cortex-R52 processor

[ARM] Add support for ARM Cortex-R52 processor

2017-07-14  Thomas Preud'homme  <thomas.preudhomme@arm.com>

    gcc/
    * config/arm/arm-cpus.in (cortex-r52): Add new entry.
    (armv8-r): Set ARM Cortex-R52 as default CPU.
    * config/arm/arm-tables.opt: Regenerate.
    * config/arm/arm-tune.md: Regenerate.
    * config/arm/driver-arm.c (arm_cpu_table): Add entry for ARM
    Cortex-R52.
    * doc/invoke.texi: Mention -mtune=cortex-r52 and availability of fp.dp
    extension for -mcpu=cortex-r52.

From-SVN: r250205