core_logic: add reset logic

Add an opcode for the MCU to reset some internal registers as well as the
coprocessor.

The SPI state machine registers should not be reset this way since the reset
opcode depends on them.  They have their own reset mechanism.
core_logic_test: Test read/write of registers

Add logic to read out the register values.
Test read/write from both sides.
core_logic: specify initial register values