use c16_t type for pm weights, as it is already same type

simplify SIMD version of precoder

nfapi/open-nFAPI/nfapi/public_inc/nfapi_nr_interface_scf.h

@@ -10,6 +10,7 @@
 #define _NFAPI_NR_INTERFACE_SCF_H_
 
 #include "stddef.h"
+#include "common/platform_types.h"
 #include "nfapi_interface.h"
 #include "nfapi_nr_interface.h"
 
@@ -488,11 +489,7 @@ typedef struct {
 } nfapi_nr_dbt_tlv_ve_t;
 
 // Table 3–62 Precoding matrix (PM) PDU (v.222.10.04)
-typedef struct {
-  int16_t precoder_weight_Re;
-  int16_t precoder_weight_Im;
-} nfapi_nr_pm_weights_t;
-
+typedef c16_t nfapi_nr_pm_weights_t;
 
 typedef struct {
   uint16_t pm_idx;