Bluetooth: controller: Add macro with minimum allowed adv. PDU size

To check if advertising PDU is empty we can compare its length to 1.
To avoid use of magic number, the commit provides a macro for that
purpose.

Signed-off-by: Piotr Pryga <[email protected]>

Author: ppryga-nordic

subsys/bluetooth/controller/ll_sw/pdu.h

@@ -32,6 +32,8 @@
 
 #define BYTES2US(bytes, phy) (((bytes)<<3)/BIT((phy&0x3)>>1))
 
+/* Advertisement channel minimum payload size */
+#define PDU_AC_PAYLOAD_SIZE_MIN 1
 /* Advertisement channel maximum legacy payload size */
 #define PDU_AC_LEG_PAYLOAD_SIZE_MAX 37
 /* Advertisement channel maximum extended payload size */