ftdi2232_spi: revert usage of DIS_DIV_5 macro

In r1872 we replaced some magic values with constant macros from
ftdi.h. Among them was DIS_DIV_5 that represents the opcode that
disables the use of the 5x prescaler on newer devices. Unfortunately
this macro was only introduced with support for FT232H and hence is
not available in older versions of the library. Revert back to using
the magic constant.

Corresponding to flashrom svn r1873.
Signed-off-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>
Acked-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>

ft2232_spi.c

@@ -360,7 +360,7 @@ int ft2232_spi_init(void)
 
 	if (clock_5x) {
 		msg_pdbg("Disable divide-by-5 front stage\n");
-		buf[0] = DIS_DIV_5;
+		buf[0] = 0x8a; /* Disable divide-by-5. DIS_DIV_5 in newer libftdi */
 		if (send_buf(ftdic, buf, 1)) {
 			ret = -5;
 			goto ftdi_err;