soc: mediatek: mtk-svs: Check if SVS mode is available in the beginning

The svs_init01() and svs_init02() functions are already checking if the
INIT01 and INIT02 modes are available - but that's done in for loops and
for each SVS bank.

Give those a shortcut to get out early if no SVS bank features the
desired init mode: this is especially done to avoid some locking in
the svs_init01(), but also to avoid multiple for loops to check the
same, when no bank supports a specific mode.

Link: https://lore.kernel.org/r/20231121125044.78642-17-angelogioacchino.delregno@collabora.com


Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>