radeonsi/vcn: optimize bitstream buffer resize logic

radeonsi/vcn: optimize bitstream buffer resize logic

bitstream buffer is unmapped, resized and mapped again if new size
is greater than the current bitstream buffer size. This will be done
for each input buffer. This patch will avoid that and do resize
only once irrespective of number of input buffers. With the new logic,
total size is calculated first and call unmap, resize and map only once.

Signed-off-by: Sajeesh Sidharthan <sajeesh.sidharthan@amd.com>
Reviewed-by: Boyuan Zhang <Boyuan.Zhang@amd.com>
Reviewed-by: Veerabadhran Gopalakrishnan <Veerabadhran.Gopalakrishnan@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22308>