drm/amdgpu: Fix parameter annotation in vcn_v5_0_0_is_idle

Update parameter description in the vcn_v5_0_0_is_idle function

Fixes the below with gcc W=1:
drivers/gpu/drm/amd/amdgpu/vcn_v5_0_0.c:1231: warning: Function parameter or struct member 'ip_block' not described in 'vcn_v5_0_0_is_idle'
drivers/gpu/drm/amd/amdgpu/vcn_v5_0_0.c:1231: warning: Excess function parameter 'handle' description in 'vcn_v5_0_0_is_idle'

Cc: Christian König <christian.koenig@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>