ti_omap5_common: Respect USB controller number in fastboot

On "fastboot reboot-bootloader" we check "dofastboot" variable and do
"fastboot 0" command in U-Boot if it's 1. But there are boards which have
USB controller number other than 0, so it should be respected when
performing "fastboot" command.

This patch reuses CONFIG_FASTBOOT_USB_DEV option toprovide correct USB
controller number to "fastboot" command.

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Reviewed-by: Tom Rini <trini@konsulko.com>

include/configs/ti_omap5_common.h

@@ -114,7 +114,8 @@
 	"if test ${dofastboot} -eq 1; then " \
 		"echo Boot fastboot requested, resetting dofastboot ...;" \
 		"setenv dofastboot 0; saveenv;" \
-		"echo Booting into fastboot ...; fastboot 0;" \
+		"echo Booting into fastboot ...; " \
+		"fastboot " __stringify(CONFIG_FASTBOOT_USB_DEV) "; " \
 	"fi;" \
 	"run findfdt; " \
 	"run envboot; " \