[nrf noup] tests: drivers: mspi: api: nRF54L15 remove device

Remove definition of dummy device since there is already external
flash defined in MSPI snippets.

Signed-off-by: Magdalena Pastula <[email protected]>

Author: magp-nordic

tests/drivers/mspi/api/boards/nrf54l15dk_nrf54l15_cpuapp.overlay

@@ -9,16 +9,3 @@
 		mspi0 = &sdp_mspi;
 	};
 };
-
-&cpuflpr_vpr {
-	status = "okay";
-
-	sdp_mspi: sdp_mspi {
-		mspi_device: mspi_device@0 {
-			status = "okay";
-			compatible = "zephyr,mspi-emul-device";
-			reg = <0x0>;
-			mspi-max-frequency = <48000000>;
-		};
-	};
-};