[console] Remove never-used putline() method

putline() was introduced back in 2007 for a feature that was never
committed.  No console driver implements it and no code calls it, so
remove it from struct console_driver.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/include/console.h

 struct console_driver {
 	/** Console is disabled.
 	 *
-	 * The console's putchar(), putline(), getchar() and iskey()
-	 * methods will not be called while #disabled==1. Typically
-	 * the console's initialisation functions will set #disabled=0
-	 * upon completion.
+	 * The console's putchar(), getchar() and iskey() methods will
+	 * not be called while #disabled==1.  Typically the console's
+	 * initialisation functions will set #disabled=0 upon
+	 * completion.
 	 *
 	 */
 	int disabled;
 	 */
 	void ( *putchar ) ( int character );
 
-	/** Write an entire line to the console.
-	 * This is intended to be used by line-oriented output media,
-	 * like system logging facilities or line printers.
-	 * Line output will not contain non-printable characters.
-	 *
-	 * @v linebuffer	Pointer to the \0-terminated line
-	 * @ret None		-
-	 * @err None		-
-	 */
-	void ( * putline ) ( unsigned char * linebuffer );
-
 	/** Read a character from the console.
 	 *
 	 * @v None		-