Initialize nr_prach_info_t structure to zero before use

This commit ensures that the 'info' structure is properly initialized
with zero values before assigning values to its members.

This prevents the use of uninitialized memory which could contain
contain garbage values.

e.g. in FR2 case we have: `info.N_RA_sfn += count_bits64(info.s_map);`

openair2/LAYER2/NR_MAC_COMMON/nr_mac_common.c

@@ -1552,7 +1552,7 @@ void set_monitoring_periodicity_offset(NR_SearchSpace_t *ss,
 nr_prach_info_t get_nr_prach_occasion_info_from_index(uint8_t index, frequency_range_t freq_range, uint8_t unpaired)
 {
   uint8_t format2 = 0xff;
-  nr_prach_info_t info;
+  nr_prach_info_t info = {0};
   if (freq_range == FR2) {
     info.x = table_6_3_3_2_4_prachConfig_Index[index][2];
     info.y = table_6_3_3_2_4_prachConfig_Index[index][3];