drm/amd/display: Fix missing parameter details in amdgpu_dm_ism

drm/amd/display: Fix missing parameter details in amdgpu_dm_ism

Update comments in dm_ism_get_idle_allow_delay() and
dm_ism_insert_record() to better reflect their behavior and inputs.

dm_ism_get_idle_allow_delay() computes the delay before allowing
idle optimizations based on history and stream timing.

dm_ism_insert_record() stores idle duration records in the
circular history buffer.

These functions explain what they do, but they do not explain what their
inputs mean.

Fixes the below with gcc W=1:
../display/amdgpu_dm/amdgpu_dm_ism.c:44 function parameter 'current_state' not described in 'dm_ism_next_state'
../display/amdgpu_dm/amdgpu_dm_ism.c:44 function parameter 'event' not described in 'dm_ism_next_state'
../display/amdgpu_dm/amdgpu_dm_ism.c:44 function parameter 'next_state' not described in 'dm_ism_next_state'
../display/amdgpu_dm/amdgpu_dm_ism.c:153 function parameter 'ism' not described in 'dm_ism_get_idle_allow_delay'
../display/amdgpu_dm/amdgpu_dm_ism.c:153 function parameter 'stream' not described in 'dm_ism_get_idle_allow_delay'
../display/amdgpu_dm/amdgpu_dm_ism.c:216 function parameter 'ism' not described in 'dm_ism_insert_record'
../display/amdgpu_dm/amdgpu_dm_ism.c:44 function parameter 'current_state' not described in 'dm_ism_next_state'
../display/amdgpu_dm/amdgpu_dm_ism.c:44 function parameter 'event' not described in 'dm_ism_next_state'
../display/amdgpu_dm/amdgpu_dm_ism.c:44 function parameter 'next_state' not described in 'dm_ism_next_state'
../display/amdgpu_dm/amdgpu_dm_ism.c:153 function parameter 'ism' not described in 'dm_ism_get_idle_allow_delay'
../display/amdgpu_dm/amdgpu_dm_ism.c:153 function parameter 'stream' not described in 'dm_ism_get_idle_allow_delay'
../display/amdgpu_dm/amdgpu_dm_ism.c:216 function parameter 'ism' not described in 'dm_ism_insert_record'

Fixes: 754003486c3c ("drm/amd/display: Add Idle state manager(ISM)")
Cc: Ray Wu <ray.wu@amd.com>
Cc: Leo Li <sunpeng.li@amd.com>
Cc: Roman Li <roman.li@amd.com>
Cc: Alex Hung <alex.hung@amd.com>
Cc: Tom Chung <chiahsuan.chung@amd.com>
Cc: Aurabindo Pillai <aurabindo.pillai@amd.com>
Cc: Mario Limonciello (AMD) <superm1@kernel.org>
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>