drm/amd/display: fix the coding style issue of integrated_info

Follow the coding style of size of a struct, changing to:

p = kmalloc(sizeof(*p), ...);

Signed-off-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>