serial: sc16is7xx: remove SC16IS7XX_MSR_DELTA_MASK

This definition isn't used anywhere anymore, let's delete it.
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Signed-off-by: Lech Perczak <lech.perczak@camlingroup.com>
Link: https://lore.kernel.org/r/91a9aa22-47b7-449a-a7ad-877ce1b6402e@camlingroup.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/sc16is7xx.c

@@ -208,7 +208,6 @@
 #define SC16IS7XX_MSR_CD_BIT		(1 << 7) /* CD (IO6)
 						  * - only on 75x/76x
 						  */
-#define SC16IS7XX_MSR_DELTA_MASK	0x0F     /* Any of the delta bits! */
 
 /*
  * TCR register bits