arm64: dts: agilex: add status to qspi dts node

Add status = "okay" to QSPI node.

Fixes: c4c8757b

 ("arm64: dts: agilex: add QSPI support for Intel Agilex")
Cc: linux-stable <stable@vger.kernel.org> # >= v5.5
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>