gas: arm: Change warning message to not reference specific A-class architecture revision

gas: arm: Change warning message to not reference specific A-class architecture revision

We noticed that a warning message about the use of scalar fp16
instructions being UNPREDICTABLE when conditionalized in an IT
block referenced the specific A-class architecture revision
ARMv8.2-A.
Many of these instructions are now also part of ARMv8.1-M, so
the warning message had become misleading.  Here we just change
the message to not specify an architecture revision at all and
update all testing accordingly.  This was done with a simple
find-n-replace within the binutils sources.  No tests have
regressed for the arm target.

gas/ChangeLog:

        * config/tc-arm.c (do_scalar_fp16_v82_encode): Remove
        ARMv8.2-A from the warning message.
        (do_neon_movhf): Likewise
        * testsuite/gas/arm/armv8-2-fp16-scalar-bad.l: Likewise
        * testsuite/gas/arm/mve-vaddsub-it-bad.l: Likewise
        * testsuite/gas/arm/mve-vcvtne-it-bad.l: Likewise
        * testsuite/gas/arm/mve-vcvtne-it.d: Likewise