Symbol based PDCCH processing

1. Refactor PDCCH PHY functions to take rxdataF of one OFDM symbol and
   produce LLR for each search space. The modified functions take
   rxdataF in a different format than that produced by nr_slot_fep(). So
   for now a memcpy is used to change the array structure. Once
   nr_slot_fep() is modified, this memcpy will no longer be needed and
   will be removed.
2. Modify DCI functions to decode DCI in the last PDCCH symbol and
   inidcate to MAC once.
3. Fix PDCCH monitoring for start symbol > 0.
4. Fix multiple PDCCH monitoring within slot.

Co-authored-by: Sakthivel Velumani <mail@sakthi.me>

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

@@ -73,6 +73,7 @@ typedef struct {
   /// frequency_domain_resource;
   uint8_t frequency_domain_resource[6];
   uint8_t StartSymbolIndex;
+  uint16_t StartSymbolBitmap;
   uint8_t duration;
   uint8_t CceRegMappingType; //  interleaved or noninterleaved
   uint8_t RegBundleSize;     //  valid if CCE to REG mapping type is interleaved type