x86/boot: simplify mode_table

There's no point in writing 80x25 text mode information via multiple
insns all storing immediate values. The data can simply be included
first thing in the vga_modes table, allowing the already present
REP MOVSB to take care of everything in one go.

While touching this also correct a related but stale comment.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>

xen/arch/x86/boot/video.S

@@ -656,8 +656,9 @@ outidx: outb    %al, %dx
 # Build the table of video modes (stored after the setup.S code at the
 # `modelist' label. Each video mode record looks like:
 #        .word        MODE-ID             (our special mode ID (see above))
-#        .byte        rows                (number of rows)
-#        .byte        columns             (number of columns)
+#        .word        rows                (number of rows)
+#        .word        columns             (number of columns)
+#        .word        0                   (color depth; gfx modes only)
 # Returns address of the end of the table in DI, the end is marked
 # with a ASK_VGA ID.
 mode_table:
@@ -666,12 +667,6 @@ mode_table:
         jnz     mtab1
 
         leaw    modelist, %di           # Store standard modes:
-        movw    $VIDEO_80x25,(%di)      # The 80x25 mode (ALL)
-        movw    $0x50,2(%di)
-        movw    $0x19,4(%di)
-        movw    $0x00,6(%di)
-        addw    $8,%di
-
         leaw    bootsym(vga_modes), %si # All modes for std VGA
         movw    $vga_modes_end-vga_modes, %cx
         rep     movsb
@@ -685,6 +680,7 @@ ret0:   ret
 
 # Modes usable on all standard VGAs
 vga_modes:
+        .word   VIDEO_80x25, 0x50,0x19,0        # 80x25
         .word   VIDEO_80x50, 0x50,0x32,0        # 80x50
         .word   VIDEO_80x43, 0x50,0x2b,0        # 80x43
         .word   VIDEO_80x28, 0x50,0x1c,0        # 80x28