Use common function to generate CSI-RS signal

The functions nr_generate_csi_rs() and nr_ue_generate_csi_rs() are
identical. This commit removes nr_ue_generate_csi_rs() and moves
nr_generate_csi_rs() to nr_phy_common_csirs.c so both gNB and UE can use
the same function.

CMakeLists.txt

@@ -939,7 +939,6 @@ set(PHY_SRC_UE
   ${OPENAIR1_DIR}/PHY/NR_REFSIG/nr_gen_mod_table.c
   ${OPENAIR1_DIR}/PHY/NR_REFSIG/dmrs_nr.c
   ${OPENAIR1_DIR}/PHY/NR_REFSIG/ptrs_nr.c
-  ${OPENAIR1_DIR}/PHY/NR_TRANSPORT/nr_csi_rs.c
   ${OPENAIR1_DIR}/PHY/NR_ESTIMATION/nr_ul_channel_estimation.c
   ${OPENAIR1_DIR}/PHY/NR_ESTIMATION/nr_freq_equalization.c
   ${OPENAIR1_DIR}/PHY/NR_ESTIMATION/nr_measurements_gNB.c