spi: intel: Update help text of PCI and Platform drivers

spi: intel: Update help text of PCI and Platform drivers

Modern intel hardware uses controllers that work in hardware
sequencing mode. In this mode, the controller exposes a subset
of operations, like read, write and erase, making it easier
and less error-prone for use.
On the other hand, most of the controllers handled by the
platform driver use software sequencing that exposes the
entire set of operations i.e. exposes the low level SPI-NOR
opcodes to the software for use.
Update PCI and Platform help text with this information.

Signed-off-by: Mauro Lima <mauro.lima@eclypsium.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Link: https://lore.kernel.org/r/20230210164158.211065-1-mauro.lima@eclypsium.com
Signed-off-by: Mark Brown <broonie@kernel.org>