cpu/cc26x0: set CPU_HAS_BITBAND

> Bit-banding is supported in order to reduce the execution time for
> read-modify-write (RMW) operations to memory.
> With bit-banding, certain regions in the memory map
> (SRAM and peripheral space) can use address aliases to access
> individual bits in one atomic operation.

https://www.ti.com/lit/ug/swcu117i/swcu117i.pdf

cpu/cc26x0/include/cpu_conf.h

@@ -27,6 +27,11 @@
 #include "cc26x0_fcfg.h"
 #include "cc26x0_prcm.h"
 
+/**
+ * @brief   Bit-Band configuration
+ */
+#define CPU_HAS_BITBAND 1
+
 #ifdef __cplusplus
 extern "C" {
 #endif