soc: mediatek: mtk-svs: Reduce memory footprint of struct svs_bank

soc: mediatek: mtk-svs: Reduce memory footprint of struct svs_bank

Many 32-bit members of this struct can be size reduced to either 16-bit
or even 8-bit, for a total saving of ~61 bytes per bank. Keeping in mind
that one SoC declares at least two banks, this brings a minimum of ~122
bytes saving (depending on compiler optimization).

Link: https://lore.kernel.org/r/20231121125044.78642-6-angelogioacchino.delregno@collabora.com
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>