bug in CH4/calculator_moore.sv

[BeeFl]

A bug in the author's Moore state machine program: undefined EQUAL state, causing the program to remain in WAIT4BUTTON state and crash.
add after line 61

last_op[Center]: state<=EQUAL;

add after line 80

EQUAL: begin
  last_op<=op_store; // Store our last operation
  state<=WAIT4BUTTON;
end