cpu: cortexm_common: remove obsolete UART0_BUFSIZE define

cpu/cortexm_common/include/cpu.h

@@ -62,17 +62,6 @@ extern "C" {
 #endif
 /** @} */
 
-/**
- * @brief   UART0 buffer size definition for compatibility reasons
- *
- * @todo remove once the remodeling of the uart0 driver is done
- * @{
- */
-#ifndef UART0_BUFSIZE
-#define UART0_BUFSIZE                   (128)
-#endif
-/** @} */
-
 /**
  * @brief   Deprecated interrupt control function for backward compatibility
  * @{