configs: atmel: fix typo in sama5d4 xplained development defconfig

The defconfig file for at91bootstrap was false:
s/sama5d4_xplainedsnf_uboot_secure/sama5d4_xplainednf_uboot_secure.

Signed-off-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

configs/atmel_sama5d4_xplained_dev_defconfig

@@ -93,7 +93,7 @@ BR2_TARGET_AT91BOOTSTRAP3=y
 BR2_TARGET_AT91BOOTSTRAP3_CUSTOM_GIT=y
 BR2_TARGET_AT91BOOTSTRAP3_CUSTOM_REPO_URL="https://github.com/linux4sam/at91bootstrap.git"
 BR2_TARGET_AT91BOOTSTRAP3_CUSTOM_REPO_VERSION="v3.8.5"
-BR2_TARGET_AT91BOOTSTRAP3_DEFCONFIG="sama5d4_xplainedsnf_uboot_secure"
+BR2_TARGET_AT91BOOTSTRAP3_DEFCONFIG="sama5d4_xplainednf_uboot_secure"
 BR2_TARGET_UBOOT=y
 BR2_TARGET_UBOOT_BUILD_SYSTEM_KCONFIG=y
 BR2_TARGET_UBOOT_CUSTOM_GIT=y