em4x70: Add write pin convenience function to write and verify a new pin

include/em4x70.h

@@ -13,6 +13,10 @@
 
 #define EM4X70_NUM_BLOCKS 16
 
+// Common word/block addresses
+#define EM4X70_PIN_WORD_LOWER 10
+#define EM4X70_PIN_WORD_UPPER 11
+
 typedef struct {
     bool parity;
 

include/pm3_cmd.h

@@ -520,6 +520,7 @@ typedef struct {
 #define CMD_LF_EM4X70_WRITE                                               0x0261
 #define CMD_LF_EM4X70_UNLOCK                                              0x0262
 #define CMD_LF_EM4X70_AUTH                                                0x0263
+#define CMD_LF_EM4X70_WRITEPIN                                            0x0264
 // Sampling configuration for LF reader/sniffer
 #define CMD_LF_SAMPLING_SET_CONFIG                                        0x021D
 #define CMD_LF_FSK_SIMULATE                                               0x021E