imx8mm: imx8mm_evk: fix BOOTSTD boot

Select BOOTSTD_FULL and BOOTSTD_BOOTCOMMAND
Correct DEFAULT_FDT_FILE
Correct env file for imx8mm_evk_fspi_defconfig

Fixes: 364ba68ed1a ("imx: imx8mm_evk: Switch to BOOTSTD")
Reported-by: Ludwig Nussel <ludwig.nussel@siemens.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/arch/arm/mach-imx/imx8m/Kconfig b/arch/arm/mach-imx/imx8m/Kconfig
index 0fe9c46..89f2b50 100644
--- a/arch/arm/mach-imx/imx8m/Kconfig
+++ b/arch/arm/mach-imx/imx8m/Kconfig
@@ -92,6 +92,8 @@
 	select FSL_CAAM
 	select ARCH_MISC_INIT
 	select SPL_CRYPTO if SPL
+	imply BOOTSTD_FULL
+	imply BOOTSTD_BOOTCOMMAND
 	imply OF_UPSTREAM
 
 config TARGET_IMX8MM_ICORE_MX8MM