NR MIMO 2x2 Support

This commit provides CSI reporting support
which is required for MIMO.  It also updates
the configuration files, provides sample BLER
simualtion files for packet dropping in the
MIMO 2x2 case. It also includes the hooks
and functions (e.g., updating UCI2_3_4 PDU field)
for MIMO 2x2 support. This commit will not include
any channel abstraction code or modelling.

openair2/LAYER2/NR_MAC_COMMON/nr_mac.h

@@ -300,6 +300,9 @@ typedef struct {
   int num_srs;
   int num_harqs;
   int num_csi_reports;
+  uint8_t pmi;
+  uint8_t ri;
+  uint8_t cqi;
 } nr_emulated_l1_t;
 
 typedef struct {