Remove HP PA-RISC atomic implementation.

Remove HP PA-RISC atomic implementation.

This architecture is obsolete and discontinued.

Support for PA-RISC can be re-added if needed, but it would be preferred
to use the GCC intrinsic support from qatomic_gcc.h (on Linux/HPPA, for
example).

Change-Id: I952e521a2c8c68840df0d44843b5487d5c20b135
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>