x86/uaccess: Remove memcpy_page_flushcache()

Commit 21b56c847753 ("iov_iter: get rid of separate bvec and xarray
callbacks") removed the calls to memcpy_page_flushcache().

In addition, memcpy_page_flushcache() uses the deprecated
kmap_atomic().

Remove the unused x86 memcpy_page_flushcache() implementation and
also get rid of one more kmap_atomic() user.

[ dhansen: tweak changelog ]

Signed-off-by: Ira Weiny <[e-mail]>
Signed-off-by: Dave Hansen <[e-mail]>
Link: https://lore.kernel.org/all/20221230-kmap-x86-v1-1-15f1ecccab50%40intel.com

arch/x86/include/asm/uaccess_64.h

···
 				unsigned size, int zerorest);
 
 extern long __copy_user_flushcache(void *dst, const void __user *src, unsigned size);
-extern void memcpy_page_flushcache(char *to, struct page *page, size_t offset,
-			   size_t len);
 
 static inline int
 __copy_from_user_inatomic_nocache(void *dst, const void __user *src,

arch/x86/lib/usercopy_64.c

···
 	}
 }
 EXPORT_SYMBOL_GPL(__memcpy_flushcache);
-
-void memcpy_page_flushcache(char *to, struct page *page, size_t offset,
-		size_t len)
-{
-	char *from = kmap_atomic(page);
-
-	memcpy_flushcache(to, from + offset, len);
-	kunmap_atomic(from);
-}
 #endif