console: Delete dummy con_font_set() and con_font_default() callback implementations

.con_font_set and .con_font_default callbacks should not pass `struct
console_font *` as a parameter, since `struct console_font` is a UAPI
structure.

We are trying to let them use our new kernel font descriptor, `struct
font_desc` instead. To make that work slightly easier, first delete all of
their no-op implementations used by dummy consoles.

This will make KD_FONT_OP_SET and KD_FONT_OP_SET_DEFAULT ioctl() requests
on dummy consoles start to fail and return `-ENOSYS`, which is intended,
since no user should ever expect such operations to succeed on dummy
consoles.
Suggested-by: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/9952c7538d2a32bb1a82af323be482e7afb3dedf.1605169912.git.yepeilin.cs@gmail.com

drivers/usb/misc/sisusbvga/sisusb_con.c

@@ -1345,19 +1345,6 @@ static int sisusbdummycon_blank(struct vc_data *vc, int blank, int mode_switch)
 	return 0;
 }
 
-static int sisusbdummycon_font_set(struct vc_data *vc,
-				   struct console_font *font,
-				   unsigned int flags)
-{
-	return 0;
-}
-
-static int sisusbdummycon_font_default(struct vc_data *vc,
-				       struct console_font *font, char *name)
-{
-	return 0;
-}
-
 static const struct consw sisusb_dummy_con = {
 	.owner =		THIS_MODULE,
 	.con_startup =		sisusbdummycon_startup,
@@ -1370,8 +1357,6 @@ static const struct consw sisusb_dummy_con = {
 	.con_scroll =		sisusbdummycon_scroll,
 	.con_switch =		sisusbdummycon_switch,
 	.con_blank =		sisusbdummycon_blank,
-	.con_font_set =		sisusbdummycon_font_set,
-	.con_font_default =	sisusbdummycon_font_default,
 };
 
 int

drivers/video/console/dummycon.c

@@ -124,18 +124,6 @@ static int dummycon_switch(struct vc_data *vc)
 	return 0;
 }
 
-static int dummycon_font_set(struct vc_data *vc, struct console_font *font,
-			     unsigned int flags)
-{
-	return 0;
-}
-
-static int dummycon_font_default(struct vc_data *vc,
-				 struct console_font *font, char *name)
-{
-	return 0;
-}
-
 /*
  *  The console `switch' structure for the dummy console
  *
@@ -154,7 +142,5 @@ const struct consw dummy_con = {
 	.con_scroll =	dummycon_scroll,
 	.con_switch =	dummycon_switch,
 	.con_blank =	dummycon_blank,
-	.con_font_set =	dummycon_font_set,
-	.con_font_default =	dummycon_font_default,
 };
 EXPORT_SYMBOL_GPL(dummy_con);