drm/amd/display: Clean up debug macros

This patch simplifies the ASSERT*() and BREAK_TO_DEBUGGER() macros:
- Move the dependency check of CONFIG_KGDB into Kconfig
- Unify the kgdb_breakpoint() call
- Drop the non-existing CONFIG_HAVE_KGDB

Also align the behavior of ASSERT() macro in both cases with and
without CONFIG_DEBUG_KERNEL_DC.

Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>