boards/chromebook-elm: force checking hashes

Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Cc: Bilal Wasim <bilalwasim676@gmail.com>
Signed-off-by: Arnout Vandecappelle <arnout@mind.be>
(cherry picked from commit 3988f2d9238bc027b5d16219867e8d3c701c0c06)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

board/chromebook/elm/patches/linux-headers/linux-headers.hash

@@ -0,0 +1 @@
+../linux/linux.hash

board/chromebook/elm/patches/linux/linux.hash

@@ -0,0 +1,2 @@
+# Locally computed
+sha256  dcdf99e43e98330d925016985bfbc7b83c66d367b714b2de0cbbfcbf83d8ca43  linux-5.10.tar.xz

configs/chromebook_elm_defconfig

@@ -35,3 +35,7 @@ BR2_PACKAGE_HOST_PARTED=y
 BR2_PACKAGE_HOST_UBOOT_TOOLS=y
 BR2_PACKAGE_HOST_UBOOT_TOOLS_FIT_SUPPORT=y
 BR2_PACKAGE_HOST_VBOOT_UTILS=y
+
+# Misc
+BR2_GLOBAL_PATCH_DIR="board/chromebook/elm/patches"
+BR2_DOWNLOAD_FORCE_CHECK_HASHES=y