mtd: spi-nor: sfdp: Fix index value for SCCR dwords

Array index for SCCR 22th DOWRD should be 21.

Fixes: 981a8d60 ("mtd: spi-nor: Parse SFDP SCCR Map")
Signed-off-by: Takahiro Kuwano <Takahiro.Kuwano@infineon.com>
Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Reviewed-by: Michael Walle <michael@walle.cc>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/d8a2a77c2c95cf776e7dcae6392d29fdcf5d6307.1672026365.git.Takahiro.Kuwano@infineon.com