drivers: spi: cc13xx_cc26xx: set power config based on SPI base addr

The power configuration is dependent on which SPI is physically used.
In order to allow DT_INST_FOREACH_STATUS_OKAY() to iterate through
instances without the assumption that index 0 corresponds to SPI0
(which would be incorrect in the case when only SPI1 is enabled),
we need to check the base address to identify which SPI is being dealt
with.

Fixes #25673

Signed-off-by: Vincent Wan <vincent.wan@linaro.org>