util: call bind_sampler_states before setting sampler_views

util: call bind_sampler_states before setting sampler_views

Fixes the following valgrind error:

    Invalid read of size 16
       at 0x28F458A1: si_set_sampler_view_desc (in radeonsi_drv_video.so)
       by 0x28F4657E: si_set_sampler_views (in radeonsi_drv_video.so)
       by 0x28D62BF5: util_compute_blit (in radeonsi_drv_video.so)
       by 0x28D3A944: vlVaHandleVAProcPipelineParameterBufferType (in radeonsi_drv_video.so)
       by 0x28D34EE1: vlVaRenderPicture (in radeonsi_drv_video.so)
       by 0x4B2582B: vaRenderPicture (in libva.so.2.500.0)
     Address 0x18142a10 is 0 bytes inside a block of size 48 free'd
       at 0x48369AB: free (vg_replace_malloc.c:540)
       by 0x28D62D51: util_compute_blit (in radeonsi_drv_video.so)
       by 0x28D3A944: vlVaHandleVAProcPipelineParameterBufferType (in radeonsi_drv_video.so)
       by 0x28D34EE1: vlVaRenderPicture (in radeonsi_drv_video.so)
       by 0x4B2582B: vaRenderPicture (in libva.so.2.500.0)
     Block was alloc'd at
       at 0x4837B65: calloc (vg_replace_malloc.c:762)
       by 0x28EFB2EC: si_create_sampler_state (in radeonsi_drv_video.so)
       by 0x28D62C30: util_compute_blit (in radeonsi_drv_video.so)
       by 0x28D3A944: vlVaHandleVAProcPipelineParameterBufferType (in radeonsi_drv_video.so)
       by 0x28D34EE1: vlVaRenderPicture (in radeonsi_drv_video.so)
       by 0x4B2582B: vaRenderPicture (in libva.so.2.500.0)

Fixes: 69430d7e59e ("va: use a compute shader for the blit")
Closes: https://gitlab.freedesktop.org/mesa/mesa/issues/2321
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3428>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3428>