os-helpers-efi: silence od stderr

When parsing an efivar value, od will complain if a given file does not
exist, such as the SecureBoot variable.

Silence stderr to ignore this.

Change-type: patch
Signed-off-by: Joseph Kogut <joseph@balena.io>

meta-balena-common/recipes-support/os-helpers/os-helpers/os-helpers-efi

@@ -21,7 +21,7 @@
 EFI_GLOBAL_VARIABLE_GUID="8be4df61-93ca-11d2-aa0d-00e098032b8c"
 
 parse_efivar_val() {
-	od --address-radix=n --format=u1 "$1" \
+	od --address-radix=n --format=u1 "$1" 2>/dev/null \
 		| tr -s "' '" \
 		| cut -d ' ' -f6
 }