docs: fb: Remove framebuffer scrollback boot option

In commit 50145474 ("fbcon: remove soft scrollback code"), the
framebuffer scrollback mode was removed, but the documentation was not
updated.  Properly update the documentation by removing the option that
is no longer present, and update the section numbering because of the
removal.
Signed-off-by: Bhaskar Chowdhury <unixbhaskar@gmail.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/436cc046a8ff9cf2a467b633527db77dc7c7de19.1600333774.git.unixbhaskar@gmail.comSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/fb/fbcon.rst

@@ -87,15 +87,8 @@ C. Boot options
 	Note, not all drivers can handle font with widths not divisible by 8,
 	such as vga16fb.
 
-2. fbcon=scrollback:<value>[k]
 
-	The scrollback buffer is memory that is used to preserve display
-	contents that has already scrolled past your view.  This is accessed
-	by using the Shift-PageUp key combination.  The value 'value' is any
-	integer. It defaults to 32KB.  The 'k' suffix is optional, and will
-	multiply the 'value' by 1024.
-
-3. fbcon=map:<0123>
+2. fbcon=map:<0123>
 
 	This is an interesting option. It tells which driver gets mapped to
 	which console. The value '0123' is a sequence that gets repeated until
@@ -116,7 +109,7 @@ C. Boot options
 	Later on, when you want to map the console the to the framebuffer
 	device, you can use the con2fbmap utility.
 
-4. fbcon=vc:<n1>-<n2>
+3. fbcon=vc:<n1>-<n2>
 
 	This option tells fbcon to take over only a range of consoles as
 	specified by the values 'n1' and 'n2'. The rest of the consoles
@@ -127,7 +120,7 @@ C. Boot options
 	is typically located on the same video card.  Thus, the consoles that
 	are controlled by the VGA console will be garbled.
 
-5. fbcon=rotate:<n>
+4. fbcon=rotate:<n>
 
 	This option changes the orientation angle of the console display. The
 	value 'n' accepts the following:
@@ -152,21 +145,21 @@ C. Boot options
 	Actually, the underlying fb driver is totally ignorant of console
 	rotation.
 
-6. fbcon=margin:<color>
+5. fbcon=margin:<color>
 
 	This option specifies the color of the margins. The margins are the
 	leftover area at the right and the bottom of the screen that are not
 	used by text. By default, this area will be black. The 'color' value
 	is an integer number that depends on the framebuffer driver being used.
 
-7. fbcon=nodefer
+6. fbcon=nodefer
 
 	If the kernel is compiled with deferred fbcon takeover support, normally
 	the framebuffer contents, left in place by the firmware/bootloader, will
 	be preserved until there actually is some text is output to the console.
 	This option causes fbcon to bind immediately to the fbdev device.
 
-8. fbcon=logo-pos:<location>
+7. fbcon=logo-pos:<location>
 
 	The only possible 'location' is 'center' (without quotes), and when
 	given, the bootup logo is moved from the default top-left corner
@@ -174,7 +167,7 @@ C. Boot options
 	displayed due to multiple CPUs, the collected line of logos is moved
 	as a whole.
 
-9. fbcon=logo-count:<n>
+8. fbcon=logo-count:<n>
 
 	The value 'n' overrides the number of bootup logos. 0 disables the
 	logo, and -1 gives the default which is the number of online CPUs.