fpga/fw: Introduce syscall TK1_SYSCALL_GET_VIDPID

Introduce new syscall TK1_SYSCALL_GET_VIDPID to get Vendor ID and
Product ID from the protected Unique Device Identification number.

UDI is protected from device apps to protect the serial number, so
apps won't know the exact TKey they are running on other than the CDI.
It may, however, be important to know what *kind* of TKey they are
running on, so we want to expose the Vendor ID and Product ID.

- fpga: Allow UDI to be read when doing syscalls.
- Add the new syscall to firmware.
- Add test to testapp directly after negative test of reading UDI to
  read out VID/PID through a syscall.

hw/application_fpga/fw/tk1/syscall_num.h

@@ -7,6 +7,7 @@
 enum syscall_num {
 	TK1_SYSCALL_RESET = 1,
 	TK1_SYSCALL_SET_LED = 10,
+	TK1_SYSCALL_GET_VIDPID = 12,
 };
 
 #endif