get_operand_value

Get number used in the operand
This function returns an immediate number used in the operand
     ea - linear address of instruction
     n  - the operand number
The return values are:
     operand is an immediate value  => immediate value
     operand has a displacement     => displacement
     operand is a direct memory ref => memory address
     operand is a register          => register number
     operand is a register phrase   => phrase number
     otherwise                      => -1

long get_operand_value(long ea, long n);