radeon/vcn: increase encoder dpb size

radeon/vcn: increase encoder dpb size

Base the number of reconstructed pictures the encoder allocates based on
the number of reference pictures to be used for encoding. Also move the
calculation and allocation of reconstructed pictures to VCN 1, from VCN
2.

v2: Add back the accidentally deleted
'two_pass_search_center_map_offset' (Boyuan)

Signed-off-by: Thong Thai <thong.thai@amd.com>
Reviewed-by: Boyuan Zhang <boyuan.zhang@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13915>