[FL-1616] RFID: fix HID emulation (#610)

* Rfid: fixed HID emulation by adding zero pulse every 4 bits
* Rfid: HID emulation fixed with DSP based FSK oscillator.

applications/lfrfid/helpers/osc-fsk.cpp

@@ -0,0 +1,20 @@
+#include "osc-fsk.h"
+
+OscFSK::OscFSK(uint16_t _freq_low, uint16_t _freq_hi, uint16_t _osc_phase_max)
+    : freq{_freq_low, _freq_hi}
+    , osc_phase_max(_osc_phase_max) {
+    osc_phase_current = 0;
+}
+
+bool OscFSK::next(bool bit, uint16_t* period) {
+    bool advance = false;
+    *period = freq[bit];
+    osc_phase_current += *period;
+
+    if(osc_phase_current > osc_phase_max) {
+        advance = true;
+        osc_phase_current -= osc_phase_max;
+    }
+
+    return advance;
+}