[Committed][Arm][testsuite] Fix failure for arm-fp16-ops-*.C

[Committed][Arm][testsuite] Fix failure for arm-fp16-ops-*.C

Since r275022 which deprecates some uses of volatile, all arm-fp16-ops-*.C
were failing with warnings of deprecated valatile uses on arm-none-eabi and
arm-none-linux-gnueabihf. This patch removes the volatile declarations from
the header. Since none of the tests are run with any high optimization levels,
this should change should not prevent the real function of the tests.

gcc/testsuite/ChangeLog:

2019-12-02  Sudakshina Das  <sudi.das@arm.com>

	* g++.dg/ext/arm-fp16/arm-fp16-ops.h: Remove volatile keyword.

From-SVN: r278905