serial: arm_dcc: Add DCC support for V7R based cores

DCC is supported on Cortex R series as well. Enable DCC support
for V7R.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>

drivers/serial/arm_dcc.c

@@ -19,7 +19,7 @@
 #include <dm.h>
 #include <serial.h>
 
-#if defined(CONFIG_CPU_V6) || defined(CONFIG_CPU_V7A)
+#if defined(CONFIG_CPU_V6) || defined(CONFIG_CPU_V7A) || defined(CONFIG_CPU_V7R)
 /*
  * ARMV6 & ARMV7
  */