get_frame_regs_size

Get size of saved registers in function frame
     ea - any address belonging to the function
returns: Size of saved registers in bytes.
         If the function doesn't have a frame, return 0
         This value is used as offset for BP
         (if FUNC_FRAME is set)
         If the function doesn't exist, return -1

#define get_frame_regs_size(ea)  get_func_attr(ea, FUNCATTR_FRREGS)