nxp: imx8ulp: change SOC name to MIMX8UD7

Zephyr PR#70219 changes i.MX8ULP's SOC name to MIMX8UD7.
As such, we need to update the board configuration file
and the SOC name inside `xtensa-build-zephyr.py` to use
the new SOC name.

Signed-off-by: Laurentiu Mihalcea <laurentiu.mihalcea@nxp.com>

Author: LaurentiuM1234

app/boards/imx8ulp_evk_imx8ulp_adsp.conf app/boards/imx8ulp_evk_mimx8ud7_adsp.confapp/boards/imx8ulp_evk_imx8ulp_adsp.conf renamed to app/boards/imx8ulp_evk_mimx8ud7_adsp.conf

@@ -139,7 +139,7 @@ class PlatformConfig:
 		RIMAGE_KEY = "key param ignored by imx8m"
 	),
 	"imx8ulp" : PlatformConfig(
-		"imx", "imx8ulp_evk/imx8ulp/adsp",
+		"imx", "imx8ulp_evk/mimx8ud7/adsp",
 		f"RI-2023.11{xtensa_tools_version_postfix}",
 		"hifi4_nxp2_s7_v2_1a_prod",
 		RIMAGE_KEY = "key param ignored by imx8ulp"