configs/microchip_sama7g5ek_mmc_defconfig: set custom linux version to 5.15.21 and add host openssl for linux

Fixes:
https://gitlab.com/ymorin/buildroot/-/jobs/2035821098

Signed-off-by: Giulio Benetti <giulio.benetti@benettiengineering.com>
Tested-by: Eugen Hristev <eugen.hristev@microchip.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

configs/microchip_sama7g5ek_mmc_defconfig

@@ -1,12 +1,16 @@
 BR2_arm=y
 BR2_cortex_a7=y
 BR2_ARM_FPU_NEON_VFPV4=y
+BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_5_15=y
 BR2_ROOTFS_POST_IMAGE_SCRIPT="support/scripts/genimage.sh"
 BR2_ROOTFS_POST_SCRIPT_ARGS="-c board/microchip/sama7g5ek/genimage.cfg"
 BR2_LINUX_KERNEL=y
+BR2_LINUX_KERNEL_CUSTOM_VERSION=y
+BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="5.15.21"
 BR2_LINUX_KERNEL_DEFCONFIG="sama7"
 BR2_LINUX_KERNEL_DTS_SUPPORT=y
 BR2_LINUX_KERNEL_INTREE_DTS_NAME="at91-sama7g5ek"
+BR2_LINUX_KERNEL_NEEDS_HOST_OPENSSL=y
 BR2_TARGET_ROOTFS_EXT2=y
 BR2_TARGET_ROOTFS_EXT2_4=y
 BR2_TARGET_ROOTFS_EXT2_SIZE="120M"