openmp: recipe cleanup

openmp: recipe cleanup

Remove perlnative inherit, this recipe does not depend on non-standard
perl (or any perl, in fact).

Remove python3native inherit, this recipe does not depend on non-standard
Python modules. python3-native will still be pulled into the sysroot via
python3targetconfig however.

Remove PACKAGECONFIG:remove:powerpc, as powerpc is explicitly marked as
not compatible later in the recipe.

Remove LLVM_ENABLE_PER_TARGET_RUNTIME_DIR, this is only used during
monolithic builds of llvm.

Remove OPENMP_STANDALONE_BUILD, this is automatically detected when
building.

Remove CMAKE_POSITION_INDEPENDENT_CODE, this is the default value.

Remove all _TOOL, these are not used.

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>