Move functions for packing/unpacking SRS.indication

Changed parameter in unpack_nr_srs_indication to void * to be inline with other unpack procedures.
Added memory allocation for pdu_list inside unpack function.

Add unitary test for SRS.indication( test pack/unpack, free, copy and compare )
Added rands16 to provide random int16_t values, needed for SRS.indication unitary test
Added constant NFAPI_NR_SRS_IND_MAX_PDU to follow constants related to other P7 messages limiting the maximum number of PDUs to use.

nfapi/tests/nr_fapi_test.h

@@ -81,6 +81,11 @@ uint16_t rand16_range(uint16_t lower, uint16_t upper)
   return (rand() % (upper - lower + 1)) + lower;
 }
 
+int16_t rands16_range(int16_t lower, int16_t upper)
+{
+  return (rand() % (upper - lower + 1)) + lower;
+}
+
 uint32_t rand32_range(uint32_t lower, uint32_t upper)
 {
   return (rand() % (upper - lower + 1)) + lower;