vt: keyboard, Fix typo in the doc for vt_get_shift_state()

Kernel documentation validator is not happy:

.../keyboard.c:2195: warning: expecting prototype for vt_get_shiftstate(). Prototype was for vt_get_shift_state() instead

This is due to typo, fix it here.
Reviewed-by: NJiri Slaby <jirislaby@kernel.org>
Signed-off-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20210303083229.75784-1-andriy.shevchenko@linux.intel.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/vt/keyboard.c

@@ -2186,7 +2186,7 @@ void vt_reset_unicode(int console)
 }
 
 /**
- *	vt_get_shiftstate	-	shift bit state
+ *	vt_get_shift_state	-	shift bit state
  *
  *	Report the shift bits from the keyboard state. We have to export
  *	this to support some oddities in the vt layer.