Drop the "pbank" pointer from struct svs_bank: this was used to simply
pass a pointer to the SVS bank that the flow was working on.
That for instance needs more locking, and it's avoidable by adding one
more parameter to functions working on specific banks, either a bank
index number, or passing the svs_bank pointer directly from the caller.

Even if the locking can now be reduced, for now, it was still left in
place for the sake of making sure to not introduce any stability and/or
reliability regression.

Link: https://lore.kernel.org/r/20231121125044.78642-12-angelogioacchino.delregno@collabora.comSigned-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>