drm/amd/display: Make BREAK_TO_DEBUGGER() a debug print

[Why]
Warnings in the kernel are generally treated as errors.

The BREAK_TO_DEBUGGER macro is not a critical error or warning, but
rather intended for developer use to help investigate behavior and
sequences for other issues.

We do still make use of DC_ERROR/ASSERT(0) in various places in the
code for things that are genuine issues.

Since most developers don't actually KGDB while debugging the kernel
these essentially would have no value on their own since the KGDB
breakpoint wouldn't trigger - ASSERT(0) was used as a shortcut to get
a stacktrace.

[How]
Turn it into a DRM_DEBUG_DRIVER print instead. We unfortunately lose
the stacktrace, but we still do retain some of the useful debug
information this offers by having at least the function and line
number loggable.

If KGDB is supported in the kernel this will still trigger a real
breakpoint as well.

Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Leo Li <sunpeng.li@amd.com>
Cc: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Cc: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/os_types.h

@@ -111,7 +111,15 @@
 #define ASSERT(expr) WARN_ON_ONCE(!(expr))
 #endif
 
-#define BREAK_TO_DEBUGGER() ASSERT(0)
+#if defined(CONFIG_HAVE_KGDB) || defined(CONFIG_KGDB)
+#define BREAK_TO_DEBUGGER() \
+	do { \
+		DRM_DEBUG_DRIVER("%s():%d\n", __func__, __LINE__); \
+		kgdb_breakpoint(); \
+	} while (0)
+#else
+#define BREAK_TO_DEBUGGER() DRM_DEBUG_DRIVER("%s():%d\n", __func__, __LINE__)
+#endif
 
 #define DC_ERR(...)  do { \
 	dm_error(__VA_ARGS__); \