spi: intel: Use correct mask for flash and protected regions

The flash and protected region mask is actually 0x7fff (30:16 and 14:0)
and not 0x3fff so fix this accordingly. While there use GENMASK() instead.

Cc: stable@vger.kernel.org
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Link: https://lore.kernel.org/r/20221025062800.22357-1-mika.westerberg@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>