spi: tegra210-quad: Add runtime autosuspend support

spi: tegra210-quad: Add runtime autosuspend support

Using Tegra234, it was found that it takes about 10us to disable clocks
and 20us to enable clocks, adding about 30us overhead per operation.
For a 4MB firmware update with 16,384 page programs, this results in
~491ms total overhead (12% impact).

With Tegra234, flash operations were observed to occur in bursts with
50-200μs gaps between page programs. Testing on Tegra234 with various
operation patterns shows 500ms delay provides optimal balance, and for
longer operations (>500ms), the overhead is negligible. Therefore,
update the driver to use pm-runtime autosuspend with the default timeout
of 500ms to reduce the clock gating overhead during consecutive QSPI
transfers.

Signed-off-by: Vishwaroop A <va@nvidia.com>
Link: https://patch.msgid.link/20260224092452.1482800-1-va@nvidia.com
Signed-off-by: Mark Brown <broonie@kernel.org>