grub: Remove native version of grub-efi

The native version of grub-efi only installs the tools

  /usr/bin/grub-editenv
  /usr/bin/grub-mkimage

to sysroots-components/, but equivalent tools are already provided by
grub-native, the difference on x86_64 being 4 hardwired paths in grub-mkimage
(values taken from grub-native):

  LOCALEDIR       = $TMPDIR/work/x86_64-linux/grub-native/2.04-r0/recipe-sysroot-native/usr/share/locale
  GRUB_DATADIR    = $TMPDIR/work/x86_64-linux/grub-native/2.04-r0/recipe-sysroot-native/usr/share
  GRUB_LIBDIR     = $TMPDIR/work/x86_64-linux/grub-native/2.04-r0/recipe-sysroot-native/usr/lib
  GRUB_SYSCONFDIR = $TMPDIR/work/x86_64-linux/grub-native/2.04-r0/recipe-sysroot-native/etc

If grub-native and grub-efi-native are built with the following patch

--- grub-2.04.orig/configure.ac
+++ grub-2.04/configure.ac
@@ -1980,10 +1980,10 @@ grub_libdir="$(eval echo "$libdir")"
 grub_localedir="$(eval echo "$localedir")"
 grub_datadir="$(eval echo "$datadir")"
 grub_sysconfdir="$(eval echo "$sysconfdir")"
-AC_DEFINE_UNQUOTED(LOCALEDIR, "$grub_localedir", [Locale dir])
-AC_DEFINE_UNQUOTED(GRUB_LIBDIR, "$grub_libdir", [Library dir])
-AC_DEFINE_UNQUOTED(GRUB_DATADIR, "$grub_datadir", [Data dir])
-AC_DEFINE_UNQUOTED(GRUB_SYSCONFDIR, "$grub_sysconfdir", [Configuration dir])
+AC_DEFINE_UNQUOTED(LOCALEDIR, "/non-existent", [Locale dir])
+AC_DEFINE_UNQUOTED(GRUB_LIBDIR, "/non-existent", [Library dir])
+AC_DEFINE_UNQUOTED(GRUB_DATADIR, "/non-existent", [Data dir])
+AC_DEFINE_UNQUOTED(GRUB_SYSCONFDIR, "/non-existent", [Configuration dir])

the produced grub-editenv/grub-mkimage binaries become binary equivalent,
assuming reproducible builds is active. Since the unpatched values of
LOCALEDIR/GRUB_DATADIR/GRUB_LIBDIR/GRUB_SYSCONFDIR point to directories that
are not expected to exist at runtime, they can be ignored.

Therefore:
 * remove grub-efi-native and instead rely on the same tools from
   grub-native
 * replace references to grub-efi-native with grub-native
 * remove unused grub-efi-native security flags overrides

Signed-off-by: Jacob Kroon <jacob.kroon@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>