drm/amd/display: Fix NULL dereference in dcn50/dcn60 init_hw

dc->clk_mgr is checked for NULL earlier in dcn50_init_hw() and
dcn60_init_hw(), but dcn50_initialize_min_clocks() and
dcn401_initialize_min_clocks() are called without any guard,
causing Smatch to report potential NULL dereferences.

Guard both call sites with the same pattern used throughout
both functions:

  if (dc->clk_mgr && dc->clk_mgr->funcs)

Also fix dcn50_initialize_min_clocks() which calls
get_dispclk_from_dentist without checking the function pointer,
unlike the dcn401 equivalent which guards that call.

Fix kernel-doc in dcn60_hwseq.c by adding missing parameter descriptions
for @probe in dcn60_update_probe_status() and @type in
is_probe_measurement_type_for_hubbub().

Fixes: 7f7d7ea1fa51 ("drm/amd/display: Add new sources for DCN6")
Reported-by: Dan Carpenter <error27@gmail.com>
Cc: Aurabindo Pillai <aurabindo.pillai@amd.com>
Cc: Ivan Lipski <ivan.lipski@amd.com>
Cc: Dan Wheeler <daniel.wheeler@amd.com>
Cc: Roman Li <roman.li@amd.com>
Cc: Alex Hung <alex.hung@amd.com>
Cc: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 325c9a827cdd748e126eafeadaffc556204773d2)