MIPS: Restore symbol versions for copy_page_cpu and clear_page_cpu

The mips build generates two warnings:

WARNING: modpost: EXPORT symbol "clear_page_cpu" [vmlinux] version generation failed, symbol will not be versioned.
WARNING: modpost: EXPORT symbol "copy_page_cpu" [vmlinux] version generation failed, symbol will not be versioned.

Add their prototypes to be defined in asm-prototypes.h, so that
genksyms knows the types of these symbols and can generate CRCs for
them.

Reported-by: k2ci <[e-mail]>
Signed-off-by: Genjian Zhang <[e-mail]>
Signed-off-by: Thomas Bogendoerfer <[e-mail]>

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

···
 #include <linux/uaccess.h>
 #include <asm/ftrace.h>
 #include <asm/mmu_context.h>
+
+extern void clear_page_cpu(void *page);
+extern void copy_page_cpu(void *to, void *from);