Fix scheduler for long prach

Long PRACH extends beyond a slot. Changes necessary to mark future slots
that may contain prach in ru, phy and mac functions.

In RU, the PRACH IDFT is done only after receiving last slot and marks
for L1 to start processing. The L1 processes at the last prach slot and
reports to MAC with the first slot index.

In MAC scheduler, the VRB for future slots are also marked as used.
PRACH scheduler is called in advance one frame minus num prach slots.

common/utils/nr/nr_common.c

@@ -1287,6 +1287,17 @@ int get_scan_ssb_first_sc(const double fc, const int nbRB, const int nrBand, con
   return numGscn;
 }
 
+// Table 38.211 6.3.3.1-1
+static uint8_t long_prach_dur[4] = {1, 3, 4, 1}; // 0.9, 2.28, 3.35, 0.9 ms
+
+uint8_t get_long_prach_dur(unsigned int format, unsigned int mu)
+{
+  AssertFatal(format < 4, "Invalid long PRACH format %d\n", format);
+  const int num_slots_subframe = (1 << mu);
+  const int prach_dur_subframes = long_prach_dur[format];
+  return (prach_dur_subframes * num_slots_subframe);
+}
+
 int get_delay_idx(int delay, int max_delay_comp)
 {
   int delay_idx = max_delay_comp + delay;