"arm_coreboot: Support DMA" breaks arm64

[Leif Lindholm]

Commit 265292f ("arm_coreboot: Support DMA") breaks arm64 grub-mkimage with:
/work/local/bin/grub-mkimage: error: undefined symbol grub_arch_sync_dma_caches.

This appears to be caused purely by the false symbol dependency
created by the non-x86 version being an EXPORT_FUNC, in order to be
usable by modules.

A not very pretty but functional workaround is:

diff --git a/include/grub/cache.h b/include/grub/cache.h
index 1c98ce2..cc4c833 100644
--- a/include/grub/cache.h
+++ b/include/grub/cache.h
@@ -40,7 +40,7 @@ grub_arch_sync_dma_caches (volatile void *address
__attribute__ ((unused)),
                           grub_size_t len __attribute__ ((unused)))
 {
 }
-#else
+#elif !defined (__aarch64__)
 void EXPORT_FUNC(grub_arch_sync_dma_caches) (volatile void *address,
grub_size_t len);
 #endif
 #endif

Thoughts?

/
    Leif