libpdbg: Fix clang warning -Wunused-function
libpdbg: Fix clang warning -Wunused-function

The *_check() functions are never going to be called.

../../libpdbg/adu.c:583:1: error: unused function 'p8_adu_hw_unit_check' [-Werror,-Wunused-function]
DECLARE_HW_UNIT(p8_adu);
^
../../libpdbg/hwunit.h:43:21: note: expanded from macro 'DECLARE_HW_UNIT'
        static inline void name ##_hw_unit_check(void) {                \

Signed-off-by: Amitay Isaacs <a505e7c038746dbeb3edcd8d146dbd515432801f@ozlabs.org>

open-power/pdbg,open-power/pdbg,open-power/pdbg