arch/arc: add copy_user_page() to <asm/page.h> to fix build error on ARC

fs/dax.c uses copy_user_page() but ARC does not provide that interface,
resulting in a build error.

Provide copy_user_page() in <asm/page.h>.

../fs/dax.c: In function 'copy_cow_page_dax':
../fs/dax.c:702:2: error: implicit declaration of function 'copy_user_page'; did you mean 'copy_to_user_page'? [-Werror=implicit-function-declaration]

Reported-by: kernel test robot <[email protected]>
Signed-off-by: Randy Dunlap <[email protected]>
Cc: Vineet Gupta <[email protected]>
Cc: [email protected]
Cc: Dan Williams <[email protected]>
#Acked-by: Vineet Gupta <[email protected]> # v1
Cc: Andrew Morton <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: [email protected]
Cc: [email protected]
#Reviewed-by: Ira Weiny <[email protected]> # v2
Signed-off-by: Vineet Gupta <[email protected]>

Author: rddunlap

arch/arc/include/asm/page.h

@@ -10,6 +10,7 @@
 #ifndef __ASSEMBLY__
 
 #define clear_page(paddr)		memset((paddr), 0, PAGE_SIZE)
+#define copy_user_page(to, from, vaddr, pg)	copy_page(to, from)
 #define copy_page(to, from)		memcpy((to), (from), PAGE_SIZE)
 
 struct vm_area_struct;