alpha: sort scr_mem{cpy,move}w() out

Take scr_memmove() out of line, make both it and scr_memcpyw()
conditional upon VGA_CONSOLE or MDA_CONSOLE (if neither is
selected, we are certain to be working with the kernel-allocated
buffer rather than VRAM and defaults will work just fine).

That allows to clean vt_buffer.h, but that's a separate story

Signed-off-by: Al Viro <[e-mail]>
Acked-by: Paul E. McKenney <[e-mail]>
Acked-by: Matt Turner <[e-mail]>
Signed-off-by: Arnd Bergmann <[e-mail]>

arch/alpha/include/asm/vga.h

···
 #define VT_BUF_HAVE_RW
 #define VT_BUF_HAVE_MEMSETW
 #define VT_BUF_HAVE_MEMCPYW
+#define VT_BUF_HAVE_MEMMOVEW
 
 static inline void scr_writew(u16 val, volatile u16 *addr)
 {
···
 
 /* Do not trust that the usage will be correct; analyze the arguments.  */
 extern void scr_memcpyw(u16 *d, const u16 *s, unsigned int count);
+extern void scr_memmovew(u16 *d, const u16 *s, unsigned int count);
 
 /* ??? These are currently only used for downloading character sets.  As
    such, they don't need memory barriers.  Is this all they are intended

arch/alpha/kernel/io.c

···
 
 EXPORT_SYMBOL(_memset_c_io);
 
+#if IS_ENABLED(CONFIG_VGA_CONSOLE) || IS_ENABLED(CONFIG_MDA_CONSOLE)
+
+#include <asm/vga.h>
+
 /* A version of memcpy used by the vga console routines to move data around
    arbitrarily between screen and main memory.  */
 
···
 }
 
 EXPORT_SYMBOL(scr_memcpyw);
+
+void scr_memmovew(u16 *d, const u16 *s, unsigned int count)
+{
+	if (d < s)
+		scr_memcpyw(d, s, count);
+	else {
+		count /= 2;
+		d += count;
+		s += count;
+		while (count--)
+			scr_writew(scr_readw(--s), --d);
+	}
+}
+EXPORT_SYMBOL(scr_memmovew);
+#endif
 
 void __iomem *ioport_map(unsigned long port, unsigned int size)
 {