[ARM] Add support for ARM Cortex-R52 processor

[ARM] Add support for ARM Cortex-R52 processor

=== Context ===

This patch is part of a patch series to add support for ARMv8-R
architecture. Its purpose is to add support for ARM Cortex-R52
processor.

=== Patch description ===

This patch adds support for Cortex-R52 as an ARMv8-R processor with CRC
extensions.

2017-06-26  Thomas Preud'homme  <thomas.preudhomme@arm.com>

gas/
	* NEWS: Mention support of ARM Cortex-R52 processor.
	* config/tc-arm.c (arm_cpus): Add entry for ARM Cortex-R52 processor.
	* doc/c-arm.texi: Mention support for -mcpu=cortex-r52.