ARM: dts: nspire: Fix arm primecell compatible string

Commit c44e0503

 ("docs: dt: fix documented Primecell compatible string")
removed the last occurrence of incorrect "arm,amba-primecell" compatible
string, but somehow one occurrence of the same is left in the nspire platform.

Fix the same by replacing it with the correct "arm,primecell" compatible.

Cc: Rob Herring <robh+dt@kernel.org>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>
Cc: Conor Dooley <conor+dt@kernel.org>
Cc: devicetree@vger.kernel.org
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Link: https://lore.kernel.org/r/20230711092617.1412815-1-sudeep.holla@arm.com
Signed-off-by: Arnd Bergmann <arnd@arndb.de>