um: Restore symbol versions for __memcpy and memcpy

If CONFIG_MODVERSIONS=y:

WARNING: EXPORT symbol "__memcpy" [vmlinux] version generation failed, symbol will not be versioned.
WARNING: EXPORT symbol "memcpy" [vmlinux] version generation failed, symbol will not be versioned.

Add <asm/asm-prototypes.h>, including the generic version, so that
genksyms knows the types of these symbols and can generate CRCs for
them.

Signed-off-by: Geert Uytterhoeven <[e-mail]>
Signed-off-by: Richard Weinberger <[e-mail]>

arch/um/include/asm/asm-prototypes.h

···
+#include <asm-generic/asm-prototypes.h>