grub_2.00: strip the sparc64 files from building

Avoid building and packaging of sparc64 specific files in the x86 builds.

Fixes Bug:
[YOCTO #6427]

Signed-off-by: Nitin A Kamble <nitin.a.kamble@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
debian: fixup2

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>