Bug-fix in Up-link with respect to PUSCH RE calculation when PTRS is enabled.

Problem STATEMENT:
- When enabling PTRS flag in ulsim, there are multiple scrambling and decoding errors
  are observed even with high SNR values
  SNR 60dB   errors_scrambling 5546/13800
  Channel BLER 1.000000e+00, Channel BER 4.018841e-01

ANALYSIS:
- While extracting PTRS RE's, the PUSCH RE count was not updated accordingly for PTRS symbols.
- This results in 0 value LLR's on same positions which cause offset issue in later processing.

IMPLEMENTATION:
* nr_ulsch_demodulation.c
- In case of PTRS symbol, respective total number of PTRS RE's are subtracted from available
  PUSCH RE's in each PUSCH Symbol processing.

TESTING
* ulsim.c
- PTRS are enabled for testing and are not enabled by default by this commit.
- Available bit count is adjusted if PTRS is enabled.

VERIFICATION
- Total Scrambling errors after gNb processing shall be only 250 bits (in K=2)
  which were replaced with PTRS at UE side while transmission.
  SNR 60.000000 errors_scrambling 250/13800
  Channel BLER 0.000000e+00, Channel BER 1.811594e-02
- After adjusting available bits in ulsim.c for error calculation
  SNR 60.000000: n_errors errors_scrambling 0/13550
  Channel BLER 0.000000e+00, Channel BER 0.000000e+00

EXTRA
- Removed white-spaces from all above mentioned files
- Added Global/vim tags to .gitignore file

.gitignore

@@ -12,3 +12,9 @@ targets/bin/
 
 # vscode
 .vscode
+
+# Tags for vim/global
+GPATH
+GRTAGS
+GTAGS
+tags