Fix 'visibility' of some CPU-specific internal macros

Fix 'visibility' of some CPU-specific internal macros

Undefine internal macros that are defined and used solely in a single
CPU-specific file.

* src/atomic_ops/sysdeps/gcc/arm.h (AO_BR_ALIGN, AO_MASK_PTR,
AO_THUMB_GO_ARM, AO_THUMB_RESTORE_MODE, AO_THUMB_SWITCH_CLOBBERS):
Undefine at the end of file.
* src/atomic_ops/sysdeps/gcc/hppa.h (AO_PA_LDCW_ALIGNMENT, AO_ldcw,
AO_ldcw_align): Likewise.
* src/atomic_ops/sysdeps/gcc/ia64.h (AO_IN_ADDR, AO_LEN, AO_MASK,
AO_OUT_ADDR, AO_SWIZZLE): Likewise.
* src/atomic_ops/sysdeps/gcc/mips.h (AO_MIPS_LL, AO_MIPS_LL_1,
AO_MIPS_SC, AO_MIPS_SET_ISA): Likewise.
* src/atomic_ops/sysdeps/hpc/hppa.h (AO_PA_LDCW_ALIGNMENT, AO_ldcw,
AO_ldcw_align): Likewise.
* src/atomic_ops/sysdeps/hpc/ia64.h (AO_T_FASIZE, AO_T_SIZE): Likewise.
* src/atomic_ops/sysdeps/icc/ia64.h (AO_INTEL_PTR_t): Likewise.
* src/atomic_ops/sysdeps/test_and_set_t_is_char.h (AO_TS_SET_TRUEVAL):
Likewise.