drm/amdgpu: Add function parameter 'event' to kdoc in svm_range_evict()

Fixes the following gcc with W=1:

drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_svm.c:1841: warning: Function parameter or member 'event' not described in 'svm_range_evict'

Cc: Felix Kuehling <Felix.Kuehling@amd.com>
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: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>