selftests: arm64: Move FPSIMD in SVE ptrace test into a function

Now that all the other tests are in functions rather than inline in the
main parent process function also move the test for accessing the FPSIMD
registers via the SVE regset out into their own function.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20210913125505.52619-9-broonie@kernel.org


Signed-off-by: Will Deacon <will@kernel.org>