UE PRACH signal generation optimization

Use memcpy in nr_prach.c to fill txdata buffer.

Remove global tables related to PRACH generation.

Add new function to compute modulo multiplicative inverse and use it
directly to get inverse instead of LUT.

Removed nr_ru table and compute the values in-place.

In UE, added new flag root_seq_computed in nrUE_config to only compute
the sequence once after new nrUE_config is received.

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

@@ -691,6 +691,7 @@ typedef struct
   fapi_nr_num_prach_fd_occasions_t* num_prach_fd_occasions_list;
   uint8_t ssb_per_rach;//SSB-per-RACH-occasion Value: 0: 1/8 1:1/4, 2:1/2 3:1 4:2 5:4, 6:8 7:16
   uint8_t prach_multiple_carriers_in_a_band;//0 = disabled 1 = enabled
+  uint8_t root_seq_computed; // flag set and used only in PHY to indicate if table is computed with this config
 
 } fapi_nr_prach_config_t;